Design the surface of the lap desk. If the desk will have a simple rectangular shape, then round off the sharp corners by sketching a curve at each corner. Cut off the corners with a jigsaw.
For decorative or themed shapes, trace the border or shape onto the wood with a pattern and a pencil, leaving behind a maximum amount of work surface space. Cut out the design in the wood with a jigsaw.
Sand the edges to a smooth finish. This will give every turn, edge and corner of the lap desk a smooth surface that will not splinter or injure the child. Wipe the lap desk's surface with dry cloth to remove the excess sawdust.
Paint or stain the surface and sides of the lap desk. Choose a wood stain to highlight the wood with a rich tone and to bring out the wood's grain through the stain. Paint the lap desk to add opaque color and to accent the lap desk's theme with vibrant colors that enliven its design shape for the child will enjoy. Set the lap desk's surface aside to dry.
Use scissors to cut a 12-by-18-inch piece of fabric that coordinates with the desk's theme.
Use an iron to fold over and press the edges of the fabrics flat toward the wrong side of the fabric.
Staple the fabric to the underside of the lap desk with a heavy duty staple gun. Line up the width and length of the fabric with the width and length of the lap desk. Staple the length sides, starting at the middle, and work your way closer to the corners. Fold over the fabric at the corner to give it a large pleat, and then staple the corners into the lap desk.
Staple only one width side of the fabric, leaving the other side open for the filling.
Stuff the beanbag filling into the fabric opening until it is full. Staple that end of the fabric close.
Cover the edges of the fabric with a narrow, decorative trim. Line up the trim to the edges, and staple it into place. Cut off the excess once the end of the trim meets the beginning.