..teak with a hole in the middle for your stack this can be cut to angle withOUT a power saw, just with a handsaw if that's what you may have. Just set it at the angle you want so it is SECURE, can't wiggle, have your line scribed by laying it level on the boat with a block to be sure it's pretty level. Mark it where it needs to be cut using a compass/pencil thingy....kind of spiling it around.

Block it, cut it. At the fixed and proper angle it's not a whole different than cutting a straight line thru a piece of wood. It's same same as a bandsaw would do. Then you would do best to have a ten dollar rasp with a rounded side on it to finish the shaping of the curve to your deck. My favorite tool among smaller rasps is the four in one.....flat rasp/rounded rasp and flat file/rounded file all on the same eight inch long rasp. A longer rasp of similar flat/rounded nature would make it a bit easier for rough out work but not necessary.

IMHO...done a lot of fiddling with a hand saw and a rasp and it's very doable in my consideration.