Cut the board into two 24-inch pieces and two 12-inch lengths.
Saw off the ends of each of the boards to create 45 degree angles.
Arrange the longer pieces parallel to each other with the shorter boards at either end to create a rectangle.
Insert nails through the corners to create a picture frame shape.
Cut the screen to completely cover the frame.
Stretch the screen over the frame, and staple it onto the frame with the staple gun.
Suspend the drying shelf above the ground on top of two bricks on cinder blocks placed under the shorter sides of the frame.
Place a second pair of bricks on top of the frame over the first bricks to hold the frame in place.