The way you are doing it is the way I was taught! And my Aunt was a quilter! We folded the back over and we made it a family affair to tie the quilts! That was over 40 years ago! I still have one thats in my closet - hasn't been used in years. My son has one that we have replaced the backing fabric twice and the Army wool blanket (batting) once. He loves it.
I never even knew about "binding" until I was nearly 50! If my Aunt was still alive, she would be chewing me out for wasting fabric making a binding when there was plenty of perfectly good backing material!
On my quilts that I use flannel, fleece or minkee on, I fold the back over to the top and hem it. You can do a search on several diferent ways to miter the corners. I reduce the bulk in mine by slicing off the corners. I can't post pictures so I'm not sure I could explain it clearly.
I no longer use a blanket for batting, but sometimes I will use flannel instead of batting. Or, if the backing is a heavy fabric, I won't use any batting.
It's your quilt, you get to decide what method you want. And opinions are like hineys - everyone's got one!