For me, the key is not keeping in one position for the whole day. That's why I chose to go with an arrangement that allows me to either sit or stand. I find myself using the standing option for about 4 hours a day. I'll use it less (sometimes not at all) if I happen to be more active during working hours. You can see details of my build here:
I think adding squatting to my set of postures should just be a matter of getting a rigid chair and squatting on that.
Finally, if you do sit, I recommend getting a seat pad designed for wheelchairs. People who can't walk must do a LOT of sitting, so wheelchair seats must be comfortable.
http://planiverse.wordpress.com/2014/01/10/building-a-sit-st...
I think adding squatting to my set of postures should just be a matter of getting a rigid chair and squatting on that.
Finally, if you do sit, I recommend getting a seat pad designed for wheelchairs. People who can't walk must do a LOT of sitting, so wheelchair seats must be comfortable.