Rip one sheet of plywood in half the long way using a table saw or circular saw to make two 24 by 96 inch pieces. These will be your wing pieces.
Draw a 36-inch square centered side to side and 12 inches from one end of the second sheet, and cut it out with the circular saw. This will be your screen window.
Attach the halves of the ripped sheet of plywood to the screen using the 2-inch hinges and sheet metal screws. Lay the screen window on a sturdy, level surface. Set one of the wing pieces along the long edge . Space four hinges along this joint evenly. Attach using the sheet metal screws. Repeat on the other side.
Stand the screen up using the wing pieces to support the screen window. Attach one floor flange at the top outside corner of each wing with sheet metal screws. Center them 3 inches from the top and 3 inches from the outside edge. Thread the pipe fully into one flange. Line the second flange up and thread the second flange halfway. Test pipe for stability.
Cut a 42-inch square from the shower curtain. Fold the edge in about 1 inch and run duct tape along all four edges. Place tape along the outside edge and fold the tape over onto the other side. This will provide a double layer of both shower curtain and duct tape on all four edges.
Draw a 40-inch square around the inside of the screen window as a placement guide for the shower curtain. Starting at one corner and pulling the shower curtain tight as you go, staple the curtain along the 40-inch square.
Paint the outside of your stage with any color or design you like. Household latex paint works best. Allow the paint to dry, then hang your two clip lights angled toward the screen from the pipe. Now, bring on the puppets and the audience.