Using .5" material cut out all the pieces, use tabs. The clean up on this project is easy.
Remove all pieces and sand off the tabs. Take the holding pieces and glue all 4 of the upright parts together using clamps. Let sit for an hour.
Sand the inside of the C shape, you won’t be able to sand it easily once it is attached to the bottom.
Glue the 4 riser pieces to the base using wood glue and clamps.
Sand the back so all the pieces are smooth and the ridges cannot be felt between the layers.
Seal the coasters and holders once the sanding is complete. Use a polyurethane or similar product that will keep water from being absorbed into the wood.
Do not use a product that will fill the entire recessed cut, that is where the cork from the coaster on top needs to rest.
Buy some self-adhesive cork pads. Amazon sells them in 4" squares. Measure out the inside of the recessed circle and cut the cork so that it rests inside of the top of the coaster below it.
Do this 4 times and make sure the sticker is centered.