I was working on a maple slab for a table top and needed to put some bowties in it for reinforcement over a crack and a few other places for aesthetics. I grabbed a few action shots of the process.
Grab your marking knife and score a line around the key.
Find the biggest forstner bit that will fit and drill out the waste.
Start working up to your knife line using a freshly sharpened chisel.
Respect your knife lines. Work up to the line and when you cant take off anymore, drop your chisel into your knife line and chop firmly down.
Glue and drive in with a c-clamp. This should be a friction fit that gives good resistance when installing.
If you take your time and respect your line, you can have joints that require no fussing with.