If there is no power, then a good old hammer and nails will have to do. 10d cement coat box nails if possible, for everything. The problem with hammer and nails is that things tend to vibrate and loosen with such a frame. Have a good heavy brace on the other side of what you're nailing, like an eight pound sledge hammer. The horizontal members of the ribs and end pieces should be cut to seven feet, ten and one half inches long.
All vertical members are to be eight feet.
This allows for the overlap of the top panels over the side panels. See Figure 2 below. Construct the ribs and ends, and using the horizontal rails, fasten the frame together. Everything must work in two feet increments, so the panels will match the frame. Be as meticulous as you can in making the frame square.