Using Biscuits With Mitered Corners

Several days ago I asked about and/or talked about my interest in learning about using dowels, One of the places that I am thinking of using them is for jointing mitered joints such as in a shadow box project. In other words the miter corners are such as you might use in the construction of the corner of a box and not in the application of a frame where the workpieces lay flat as in a picture frame for example.

Anyway, Harry posted to my thread said that he liked to use biscuits and I responded that I have used biscuits in that type of joint. With all of that said, my question to Harry and others that use biscuits for this type of joint is this. My biscuit cutter works best when cutting the slots in the workpieces with cutter setting on a 90 degree edge and not so well on 45's. the only way that I have been able to cut the slots for the biscuits is to put two workpieces back to back so the the ends of the workpieces
form a 90 degree shape and this allows the cutter to have the 90 degree profile that is required to make the cuts. Hope you follow what I'm attempting to describe.

My question is that I'm wondering if there is another and/or a better way to cut the slots for the biscuits in such a joint? Because this approach is a little cumbersome has caused me to think about the possibility of using dowels instead of biscuits but don't kow if there is a doweling jig that could be used or not, seems like I saw a demo of a jig for this application, but can't seem to find it again. Sooo, if anybody has any ideas and/or thoughts along this line of thinking, I'd like to hear from you. Thanks,

Jerry