Use either velcro, elastic straps, or small magnets. I've used all of the above and they each work for different sizes. Maybe elastic and magnets would work together. Give it a try and experiment around. It's not a science.
I also tend to cut mine open on the thumb side. This side is what causes the hand to not fit. (If you had no thumb your hand would fit in fine.) The back of the hand may not be the best place, but give it a try anyway. Don't be afraid to fail and learn. It's how you improve. Keep up the good work!