I tried making my own Miter box for this job, but wound up paying $75 for this little box from www.Stewmac.com . I spent about 4 hours trying to design a similiar box out of wood but I couldn't get it to make accurate cuts. It was worth the $75 with the accuracy you get. I also bought the notched template for a 25.5" inch scale length which makes this process a breeze.
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