How to DIY a Wood-Framed Mirror

Cut a 45-degree miter on each of the blanks going opposite directions. Then cut four 5-inch long pieces. The four pieces from each blank will form the frame top/bottom (A) and frame sides (B) (Project Diagram, Cutting List).

The tongued corner (C) and grooved corner (D) will need to be fitted together with the other parts to get the final dimensions (Project Diagram, Drawing 1). Place a frame side and a frame top/bottom against the remnant blanks with the tongue and groove engaged and the tips of the side and top/bottom touching each other.

At three of the corners a small section of the tongues need to be removed (Project Diagram, Drawing 1). Dry assemble the parts shown and use a pencil to trace the sections of tongue that need to be cut away.

From the remaining section of pattern board, use a jigsaw to cut the board along its length to make blanks for the rails (E) and stiles (F)  (Project Diagram, Cutting List and Cutting Diagram). A table saw will do this quickly, but these parts don’t need to be perfect. Then cut the rails and stiles to length.

What Will Hold Wood To a Mirror?
In order to keep the mirror in place stiles and rails are needed to reinforce the frame (Project Diagram, Drawing 2) and create a pocket for the mirror.

Mark a rectangle on the back of the frame 2-1/2 inches from the sides of the inside opening for the stiles, and 1-1/2 inches from the top and bottom of the opening for the rails. Lay the mirror on the back between the marks to check that it fits.

Lightly sand the polyurethane with a fine-grit sanding sponge and apply a second coat of the semi-gloss finish.