Good Question
Woodworking
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If you don't care about species you can buy a big bundle of several dozen shims from the hardware store. If you're doing nice wedged tenons in furniture... yeah - good question.
Do you have a table or band saw? The miter guage, set to half the desired angle, would work well. Flip the stock with each cut.
What did you use? I'd use a table saw with an angle and cut along a piece of wood, then chop them up with a miter saw.
Are you trying to achieve clean consistency (so you can stack and glue them as part of a finished product)?
If so, I think your best bet would be a sliding jig on the table saw.