I am admittedly not only un-handy, but not terribly interested in learning to be handy either. Best bet if you truly have no inclination to build is to hire a shed builder/woodworker that can build something to your specifications.
(I did end up assembling my own nest box and roosts but even then I had someone else cut the wood for me, so I only screwed things together.)
(I did end up assembling my own nest box and roosts but even then I had someone else cut the wood for me, so I only screwed things together.)