This weekend I took Woodworking 2 and 3 classes at Maker Nexus.
In Woodworking 2 we built bullroarers (left item). First, we split a block lengthwise on the larger bandsaw. Then we honed down the shape using a smaller bandsaw. On a disk sander we smoothed the shape, then created an aerofoil effect through careful sanding at an angle. That 3D shape was further worked on through handsanding. An opening for the string was created on a drill press. Spin it on the string and you get a nice loud wooshing sound.
Woodworking 3 was entirely on routers. We used a table router to create a nice edge on a board, then a slot. On a second board we routed out a slat to form a joint. That's the right item. We also used a hand router to form an edge on a larger board. Apparently the technique is super versatile, the instructor recommended taking a look at YouTube videos.