How do people cut sharp inside corners, like the triangles shown? This example is cut in stone but I have seen similar features on wooden building blocks.
If we're talking tight tolerance, you could custom broach it, use a wire EDM, a sinker EDM, or live with a small radius from whatever your smallest diameter endmill is.
For wooden building blocks with larger tolerances it's a little simpler, likely a scroll saw or bandsaw.
Anyone else, please chime in if you know of additional options!