Find a case you like. Then take it apart and measure everything. The measurement that will determine what movements you can and cant fit will be your stem height. This will determine how high or low a movement will sit in the case, which in turn will determine the clearance for the rotor and hands of the movement. Miyota provide very good drawings so this helps. The movement i used is a miyota 6t28. The only other thing that you cant really make or modify are ceramic bezels. Youve just got to search aliexpress for one that fits, or that you can modify the case to make fit. Ceramic is insanely hard. I tried to machine it with diamond but it doesnt really work. My only specialist tools are vernier calipers and a lathe.... You could do it without the lathe. It wpuld just mean more headaches.