Ground Floor
The first carpenter is held relatively close to your starting point in Gerudo Prison. For some reason, the guards saw fit to leave your weapons and equipment with you, so you can use the longshot on the wooden ledge above the window to escape the prison. Stand there and look down; you will see three guards walking their routes. If you can shoot them with arrows, you don't have to worry about them. Go into the door on the left when you jump to the ground; when you turn the corner, you will find the first carpenter in a cell. Talk to him, defeat the Gerudo who appears and release him.
South Side
Continue through this area, and you'll emerge at ground level. Take the door to the left into the next section of the fortress. When you turn right, stop and aim at the far corner; a guard will approach, so shoot her with an arrow. Proceed and take the next right up the ramp and onto the roof of the fortress. Around the corner is a guard. Position yourself so you can see her walking, and when her back is turned quickly jump onto the ledge and go through the door. The second carpenter is in the cell with blue trim over the door. Keep going this way after you free him.
Top Floor
When you come out, turn right and proceed through the door. Aim your longshot at the farthest beam to get to the other side of the gap. Follow the ramp upward, go outside and jump down to the next door you see. Once you get inside, stop and aim for the corner until you see a guard. Deal with her and go down the passageway to the right. You'll come to a dead end in a room with the third carpenter. His cell has dark green trim over the door. After you free him, you have one carpenter left to rescue, so backtrack and dispatch the guard again.
Northwest
Once you make it back out onto the ledge, look to your right and jump down. You should be overlooking the front entrance of the Gerudo Fortress. Another door will be to your right, so take it and follow the path downward. You'll come to a fourth cell with beige-green trim. This holds the final carpenter you have to rescue. Afterward, the Gerudo leader will appear and give you a Gerudo Membership Card, which grants you access to the training ground, the horseback archery range and the desert.