Measure the size of the countertop. Build it one inch bigger at each exposed end. This will allow it to hang over the cabinet.
Cut the wood to length using a chop saw. You will need enough wood pieces to glue up for the width. If you need to cut one piece to width, use a table saw.
Place the wood pieces on a flat surface. Match the patterns in the grain as best you can. Try to avoid obvious seams in the wood. Mark the boards in a numbered format so that you know how the boards should be glued together.
Place the boards into the clamps. Apply a small amount of wood glue to the edge of the boards. Tighten the clamps while making sure the boards are lined up. Allow the glue to dry for 30 minutes before removing the clamps.
Sand the seams of the countertop using an orbital sander and 180 grit sandpaper. Sand out any dents or scratches in the wood.
Stain the wooden countertop with oil base stain of your choice. Allow the stain to dry for 8 hours before applying two coats of a clear sealer with a paint brush.