How far from the back wall are your speakers?

The proper distance from the front of the speaker cabinet to the wall behind the speaker is entirely dependent on the particular speaker and it's interaction to your particular room.

Unless your speakers are specifically designed to be placed right up against the wall (ex. Audio Note, Larsen, etc) you will need to use a little trial and error. I have not yet found a formula or modelling application that is 100% accurate.

This depends on the design of the speakers.

My preferred distance would be 1/3rd into the room, with my listening position 2/3rd into the room. In my room 1/3 is not feasible for the speakers so I use 1/5th the distance and 2/3rd for the listening position. This was the starting point, and small adjustments from there were needed to dial it in.

I am using Wavetouch Grand Teton speakers as LR main speakers in 15'w x 21'L x 8'h room. 3ft from the wall to back panel of Grand Tetons. My ears (listening position) are 11ft from tweeters.

That's the front wall; the back wall is the one behind your head. Mine are 30 inches from the front wall.