I made this as a retirement gift for a friend of mind that is looking forward to lots of future golf time. This needs to be made with a soft wood that has little grain. Cypress or Basswood works well. The dimensions of the block you want to start with are 5” x 1 ¾” x 1 ¾”. Leaving ¾” at the ends, drill out both ways with a 1 ¼” forstner bit.
Cut between the 1 ¼” holes with a scroll saw to create the final shape. You can shape and sand the inside now, but don’t bother sanding to a fine finish, because the grain will rise, in the next step, when you put the block in water.
Now you want to set the block, sideways, in ½” of boiling water for at least 15 minutes. This will soften the wood enough for you to be able to push the golf ball into the cavity.
Let the wood dry overnight. Drill a hole in the bottom, clear through, for the golf tee. Then you can do a finish sanding.
I used some “Tru-Oil” only on the outside, to dress is up a little.