This may be obvious, but don't expect them to fly through a small entrance.
Give them a nice porch or bar or something to land on, then they can walk through the door.
Or else skip the floor of the coop and maybe some of the walls, and just build it as a roof and roosts, supported by your climb-proof posts. That way they could fly up from any point and land on the roosts. Depending on the weather, they might be just as happy without solid walls and a solid floor.
Give them a nice porch or bar or something to land on, then they can walk through the door.
Or else skip the floor of the coop and maybe some of the walls, and just build it as a roof and roosts, supported by your climb-proof posts. That way they could fly up from any point and land on the roosts. Depending on the weather, they might be just as happy without solid walls and a solid floor.