(...) Cut a piece of linen board to fit neatly over the bottom of the inside then cut strips to cover the sides and fix in place with double-sided tape.

Place the covered slip on the box with glass on top, then place the frame over this and turn the entire thing over.

Fix with Framer's Points as shown (or flexi-tabs) and staples and tape up neatly.

Complete the job with those handy little foam-board hangers from Lion Picture Framing Supplies. Easy!