I've been building my chicken coop. I started the last week in February and am almost done now, mid April. I built the Purina chicken coop plan. I modified it a to be a little smaller 3x4 since that's what my husband was ok with.
I'm torn at this point if I wish I hadn't made the coop smaller. I'm not very strong, so I'm not sure I would have been able to handle building the slightly larger coop. On the other hand, I ended up with 5 chickens, so at least one of them will have to go.
I strongly recommend having a miter saw and jig saw for building the coop. It was a million times easier cutting the lumber with the miter saw than trying to use a circular saw and straight edge.
One thing that worked well for me was to attach the legs to the floor, we set the floor on a bench we had then attached the legs. We were able to get the legs all at the same height that way.
The other thing I learned is that this coop cost a lot more than planned. It wasn't the wood either. The screws, nails, hinges, and locks really add up fast. I ended up using two boxes of roofing nails and three and a half boxes of deck screws. Plan on it costing about double what you think it should.