I made one of these for a colleague of my husband's. 4x4 post ((about 5' high - it went into a run 6' high made out of 12'X6' high construction chain link panels - with some across the top, too)
I made it with 2x4 'arms' ( 3 of them - the bottom one was just under 5' long (so a little over 2' each side of the upright 4x4), the next one was 4' long and at the other 'face (so 90 degree angle to the first), and the last one was the parallel to the first...but on the other side of the post and was maybe 3' long, so about 14-15" each side of the 4x4.
To keep the post stable, I used 4 ~ 4' long 2x4. Had one end even with the 4x4 post edge, screwed to post, rotated the post 90 degrees, put the next one on, etc...so they 'spiraled/fanned' out from the post from all 4 sides. (I also put on the post above the last roost a picture hanger bracket (the long, jagged upper edge one) on 2 sides so a small feed/water cup could be put up there for a 'safe' feeder/waterer. I made this when I gave the colleague 2 young pullets last year- so they had an 'escape' place with food until they integrated with his other 2 older hens.) - there was no other place in their run to hide/get away.
Aside from the 4x4 post (which was pressure treated), the other 2x4s were from pallets (including one long 6' pallet!), and I used an eco-friendly, non-toxic treatment for them. (The guy would dismantle the run and move the coop to a carport type area that was fenced in for the winter, and didn't want the post permanently sunk into his lawn...and he would periodically move the pen during the 'growing' season'...so it needed to be moveable.
Sorry, I don't have pictures of it.