I collected a number of common positions out of the books and the describe of their uses. This is not a complete list, just the most frequently positions. There are many more positions named or unnamed in the books and beside that some, that only exist online which I don’t mentioned here. If you think I forgot a important position, don’t hesitate to add it here

Bara
The slave moves to lay facedown upon the floor, forehead lightly touching the floor, legs straight with ankles crossed and wrists crossed at the small of the back
"Bara, Kajira!" he said. She rolled quickly to her stomach, placing her wrists behind her, crossed, and crossing her ankles, ready to be bound.
Explorers of Gor p77
Belly
The slave moves to her belly, hands palms down near the sides of her head, forehead to the ground and waits for further orders
"Stop," he said. "To your belly."
Then I was on my belly, on the tiles, my hands at the sides of my head, prone, before his curule chair.
Kajira of Gor p427
Bracelets
In this standard binding position the girl turns to face away from the Master, back and shoulders straight, wrists held at the small of the back for ease in attaching slave bracelets
"Bracelets," he snapped. She put her head in the air and placed her hands behind her back.
Hunters of Gor p146
Capture Position
The slave lays down upon her back, bending her knees to place her feet flat against the ground, hands at her side and remains motionless
"On your back," he said, "knees raised, heels on the floor." I then lay before him, in a standard, supine capture position.
Kajira of Gor p422
Display Position
Stands, feet about shoulders width apart, fingers laced behind the neck with elbows back, head up and eyes lowered.
The auctioneer did not strike her with his whip. He merely took her arms and lifted them, so that the position chain, attached to each side of the sales collar lay across her her upper arms. Then he had her clasp her hands behind the back of her neck, so that the chain, on each side of the collar, was in the crook of her arms, and she was exposed in such a way that she could be properly exhibited.
Explorers of Gor p36
Hair
The girl stands and bows at the waist, letting her hair fall forward for display, to be seized or for any other purpose the Master might require. Another varient of this position sometime used is for the slave to stay in her previous position just bowing her head and letting her hair dangle before her for whatever use required.
I held my left hand open, at my waist. She stiffened, and looked at me, angrily. I opened and closed my left hand once. I saw her training in Gorean customs had been thorough. But she never thought that such a gesture would be used to her. She came beside me, and a bit behind me, and, crouching, put her head down, deeply. I fastened my hand in her hair. She winced. Women are helpless in this position.
Beasts of Gor p409
Heel
The slave goes to the Master's left if He is right handed, right if left handed and about one and a half paces behind Him. She follows His movements from that point.
Collar/Submission
Sometimes referred to as the collaring position or posture of female submission.In this position the slave kneels at the Master's feet and leans her body back, sitting upon her heels, with her arms extended upward, crossed at the wrists, and her head beneath them lowered in supplication.
"Assume the posture of female submission," I told her. She did so, kneeling back on her heels, her arms extended, wrists crossed, her head between them, down. She was weeping.
Tribesmen of Gor p359
Lesha
Kneel, thighs well parted, back straight or slightly arched, head held high, chin tilted to the left, hands at back with wrists crossed. This position is used to clip a leash onto the collar or for simple display/inspection of a slave girl.
"Lesha," snapped the second officer to the blond girl. She spun from facing him, and lifted her chin, turning her head to the left, placing her wrists behind her, as though for snapping them into slave bracelets.
Explorers of Gor p76
Nadu
kneel with thighs spread wide, back held straight or arched slightly, breast thrust forward, head held high with eyes lowered, sitting back on heels, hands resting palms up or palms down on thighs. Palms up was considered a plea for rape in some circumstances.
Come now, my pretty slaves,' said Ginger, "kneel straight. Back straight, heads up. Back on your heels there! Spread those pretty knees. Yes, that is the way men like it. Put your hands, palms down, on your thighs. Good. good. Excellent!" The girls now knelt in the coffle as pleasure slaves.
Savages of Gor p155
"Nadu!" he snapped. She swiftly turned, facing him, and dropped to her knees. She knelt back on her heels, her back straight, her hands on her thighs, her head up, her knees wide. It was the position of the pleasure slave.
Explorers of Gor p77
She_Sleen
moves to knees and elbows, hands clasped over your head, bottom in the air, ready for either being beaten on the bottom or being taken from behind like an animal
He knelt me there. "Put your head down, to the floor," he said. "Clasp your hands, firmly, behind the back of your neck." "Yes, Master," I moaned. He was then behind me. He put his hands, under my arms, on my breasts, sweetly and firmly. Then he moved his bands back, caressing my flanks. My head was down. My fingers were together, behind the back of my neck. I was in his collar. It was steel, I could not remove it. I belonged to him. My body hurt, from his whip, that of my master. My head hurt, from my hair, where I had been conducted, unceremoniously, to this location. "Please, Master," I sobbed. "Not like this! Not you, please!" "The slave is pretty," he remarked. "Oh!" I cried. "Oh!" "You have a lovely ass," he said. "Ohhh!" I said. "You may thank me," he said.
Kajira of Gor p434
Slave Lips
turn toward person who commanded it, purse lips and remain immobile until your freed from immobility with a kiss.
Similarly, I was not required to respond to certain sorts of commands, for example, to make "slave lips," pursing my lips for kissing, or to writhe slowly before my viewers.
Kajira of Gor p224
Standard Binding Position
When ordered into standard binding position the girl lays on the ground, wrists crossed behind the back and ankles crossed. (this is most likely another name for bara)
"Standard binding position," he said. I was prone. When a girl is prone, the standard binding position is to cross the wrists behind the back and to cross the ankles. I took this position instantaneously.
Slave Girl of Gor p125
Submission
kneels, bends at the waist, places cheek to the floor, takes the Master's right foot and places it upon her neck, places arms behind back, crossing them at the wrist.
Sula
lay on back on the floor, spread feet shoulder_width apart, and rest arms with palms up at sides, left knee flexed slightly to enhance the view. Keep eyes lowered and await inspection
"Sula, Kajira!" said the man. She slid her legs from under her and lay on her back, her hands at her sides, palms up, legs open.
Explorers of Gor p77
Tower Kneel
see nadu, alteration: knees are closed and thighs are pressed closely together (this position is used most often used to serve Mistresses)wrists may or not be crosses as your owner decides.
The position of the Tower Slave, in which Vika knelt, differs from that of a free woman only in the position of the wrists which are held before her and, when not occupied, crossed as though for binding...."
Priest Kings of Gor pgs46_47
Whipping Position
quickly drops to knees, and place forehead to the floor, hips raised high, cross arms across belly fingers gripping your sides.
I went to Targo, trembling, and knelt at his feet... I crossed my wrists beneath me and touched my head to the floor, exposing the bow of my back. It is the submissive posture of a slave girl who is to be punished. It is called Kneeling to the Whip.
Captive of Gor p200