You any relation to Dave? Just wondering.
When you say "at an angle", do you mean not directly across the grain or with the grain but instead cutting diagonally across the grain, or do you mean a sliding dovetail that rises out of the wood, or do you mean the sliding dovetail is shallower on one side than on the other as in a sliding dovetail carrying a platform between tilted uprights?
The first two could be done easily with a router and dovetail bit, while the third would be a challenge with that same router.
In the first case, you could very easily clamp a temporary straightedge to the workpiece and follow it with a handheld router. In the second case, you might cut a wedge-shaped platform on which to slide the router so as to lift the bit gradually out of the wood as you slide the router (still guided by a straightedge) in the intended direction. Its the third case that's likely to challenge your imagination and skill.
Have I caught the gist of your question? Have I answered it? Is this, perhaps, for a mount of some kind to hold a drum?
-- Tim --
Argue for your limitations,
and sure enough - they're yours.
- Richard Bach -