Cut a piece of floor molding to a width that fits where you want to place the chalkboard. Cut the left end and right end of the molding at 45-degree angles so the top edge of the molding is longer than the bottom edge. The piece of molding resembles the top of a picture frame.
Cut two pieces of floor molding that fit the desired height of the chalkboard. Cut one end of each board at a 45-degree angle and cut the other at a 90-degree angle. Cut the 45-degree angles so you can butt the top piece of molding and these two pieces of molding to create the top and sides of the chalkboard frame.
Cut a piece of 3-by-3-inch pine board to the same width as you cut the floor molding in step one. Cut both ends at a 90-degree angle. This piece of board serves as the ledge and bottom piece of the chalkboard frame.
Stain all four pieces of wood with wood stain and a rag. Wipe the excess stain off the board, then wait at least 24 hours for the stain to dry.
Place construction adhesive on the back of the first molding you cut and place the molding on the wall. Use a level on top of the molding to ensure the trim remains straight.
Glue the two pieces you cut in Step 2 to the ends of the first molding. The 45-degree angles must butt together to create 90-degree angle bends. At this point, you have the top and both sides of a rectangle frame glued onto the wall.
Glue the 3-by-3-inch pine across the bottom of the rectangle so the top of the pine rests flush against the bottom of the vertical boards you glued. This finishes the rectangle frame.
Tape off the inside edges of the wood with painter's tape.
Paint the wall inside the rectangle with chalkboard paint. You may use chalkboard spray paint or paint you roll on with a paint roller. Wait 24 hours for the paint to dry, then remove the painter's tape.