If you were going to buy a mitre jig, which one would you buy, I have tried to make my own twice now and I just cant get it so I'm putting my hands in my not so deep pockets, £150 maybe a bit more if the other half doesn't read this post
Personally I wouldn’t bother with a jig cut them by hand then make yourself a shooting board to true them up.
It doesn’t matter how I cut a mitre they always get a once over on the shooting board