Goop (shoe Goo, AquaSeal, Seam Seal) works but you have to make sure that the bottom of the boot is CLEAN! I'd give it a couple of wipes with alcohol after you get it clean, before applying to goo...

BUT the best option I've seen here is to take it to a professional shoe repair and let them do it. They have the proper glues and the clamps. It's your best bet. You may as well do it right the first time...and it's about the same cost as a tube of glue.