I am very excited to see this, what a great idea! I decided to do this too. I bought 10 Kitty litter boxes at dollar tree for 1$ each. I then built the tower according to size of pans. It is finished and ready to go. Just waiting for Barley to arrive. I order some (Cover) barley online. Tractor supply doesn't start putting it out til next week or so.
Not difficult to build, but recommend as you build it, use only one screw/nail at each connection for easy adjustment/leveling each shelf. Then after all complete and correct, put in extra hardware. Draw you plans out first, with measurements. Make sure your rails are all the same thickness. End pieces don't really matter, but should be a tad lower than the rails to not catch the handle or edge. I also put adjustable slider feet on it for fine tune adjusting on a flat floor and if I move it elsewhere. This was not difficult to build with all scrap wood. I used 2 x 2 corner posts, and 1/2 x 2 scraps for rails. I can't wait to get started! Thank you for sharing this great idea.