Plug in a hot glue gun, then cut 1/4-inch plywood into 3-inch-wide strips using shears.
Lay the first plywood strip at the back left side of the counter, flush with the end. Apply a 1/4-inch bead of hot glue across the end, then apply a second strip of plywood at the end of the first, overlapping the hot glue to hold the pieces together. Continue adding additional strips as needed to extend them all the way down the back of the counter.
Measure the distance from the rear strips to the front edge of the counter and cut two more strips to this size. Attach them at either end of the counter, perpendicular to the back strips.
Install a strip of wood along the front edge using the same technique and multiple boards if required. You should now have a rectangular shape.
Walk to the sink area and apply wooden strips around the entire perimeter, overlapping each strip edge so you can glue them together.
Apply more strips of wood around any other projections or openings in the counter using the same method as with the sink.
Clamp all areas to which you applied glue to hold them together until the glue fully dries.
Write labels on each of the wooden strips using a black permanent marker to assist the fabricator. Label the “rear wall,” left and right sides, as well as the locations of any seams.
Wait at least 30 minutes, then remove all clamps from the wood. Take pictures of the template to serve as a reference for the fabricator. Then pick up the template gently and take it to the fabricator so he can cut your Corian counter.