You can use rubber bands or twine. Also, wedging the two sections works well.
Shoo Goo is great stuff and can be used for lots of other equipment or around the house repair.
I've used it for years to rebuild worn sections of running shoe outsoles and is perfect for filling the cap between loose toe caps on lightweight hiking boots.
2 tips: Be sure that after you apply the S.G., the item being repaired is in the proper position relative to gravity. S.G. goes on like molasses, but will always settle. You want to be sure the boot is oriented the way you want it.
Also, using a toothpick to poke the S.G. down into crevices of the repair assures that the slow moving adhesive won't start setting-up before it seeps into all the openings.