The angular cuts were made with a compound miter saw, set to make 60 degree cuts.
Step 1: The Ends Are Equilateral Triangles, 60 Degree Cuts, Made From 1x2s.
Step 2: Added Triangular Pieces of 1x4s for Additional Bracing.
Step 3: The Rest of the Frame Is Two Rectangles, Hinged at the Top.
Having the two rectangles hinged together makes this cage easy to transport when knocked down. I used 3 hinges, equally spaced, to hinge the rectangles, and two hinges for the hatch. The two hinged rectangles are connected to the equilateral triangles by 6 bolts, 6 wing nuts and 12 washers, all stainless steel.
Step 4: Added a Hatch.
The horizontal piece to which the hatch is attached (also salvaged from a pallet) is joined to the rest of the frame using pocket hole screws and glue (not shown), the holes made with a Kreg-type pocket hole jig.
The handle for the hatch does double duty as a stop to keep the hatch in the correct position. I added two latches, one on either side of the handle. One would probably suffice.
The chicken wire is affixed to the frame using nail-in staples (I don't have a staple gun).
Be careful with the cut ends of the chicken wire - tuck them out of the way so no one gets injured handling the cage.