Sand the surface of each post until the corners are smooth. This gives a finished look to the stand when completed.
Apply stain to each piece of the stand according to the instructions on the can. It doesn't matter which side of the square will be facing up when this step is completed. Allow the stain to dry according to the manufacturer instructions.
Lay the plywood piece on a flat surface. Apply wood glue to each corner and to the ends of each post. Mount a post to each corner of the square so the glued ends are touching the plywood. Make the ends flush. Allow the glue to dry for 24 hours.
Flip the stand upright. Set the stand on its legs. Apply glue to one side of the butcher block and the top of the stand. Set the butcher block on top of the stand so the ends are flush. Allow the glue to dry before setting the microwave onto the stand.