The construction takes place by building the 4 flat panel wall and bottom flat panel frame. Begin with the bottom frame, laying it out on a large flat surface. Next, lay out the two gable end walls, making sure that they are the same size and that the plywood triangle pieces have the same angles. Follow this with the 2 long walls. The plywood that makes up the exterior of the roost box is attached to the flat panels at this stage. Don't forget to cut in the cleanout and egg doors as well. The plexi-glass can be installed at this time.
Once you have built the 5 flat panels, stand them up on the flat panel floor frame and check your dimensions. If all lines up properly, lay the panels down again and install the wire over them. Before installing the wire, make sure that the diagonal measurements of each frame are equal to insure that the corners are square. This is a old carpenter's trick. After the wire is secure, stand the wall up again over the floor frame and secure the corners with screws or angle brackets.
Next, complete the three interior wall of the roost box. You will need to install additional framing inside the coop to support the plywood pieces. Install as needed. Then, install the bottom of the roost box, followed by the front interior panel with the sliding door. Finally, install the top flat plywood ceiling with the vent holes.
Finally, install the roofing material and all the trim, hinges, roost bar, etc.
This sequence is only one of many ways to build this coop. I suggest you carefully think through each stage of construction, taking into account your physical limitations. There is not perfect sequence, but with a little forethought, you will greatly reduce the inevitable frustration that comes with such a building project. Stay focused when building, but stop occasionally to plan ahead.
Some like to prefinish the wood before assembly. I like this idea. I cut the framing members, then coated them with the Lifetime Wood Preservative. I gave the plywood a single roller coat of paint before cutting it as well.