To get your grafting stock you need to clip the tops now. you want growth that occurred last year. Put that in the fridge with a damp paper towel. Don't forget to mark it.

Don't cut the tree off yet. once buds are opening on other trees cut these off and graft to the stump. (you can't keep the scions long enough to wait for a graftable size sucker, although I guess if you have enough clippings you can try it as a backup)

So you are going to cleft graft into the stump. You will need to cut into some good cambium. If it is chewwed right at the ground dig down a bit to expose some workable bark/cambium. That would not be ideal but it is your only option at this point.

read and watch youtube on cleft grafts. let me add that many of the grafts on youtube are done by first time grafters and many probably fail, so look for the videos from the professionals. One detail commonly not made clear enough is the length if the connection. If you have it, you need more then and inch of contact length. Keep us posted on it