Use tweezers to peel up any adhesive left behind on the lower case.

Clean all traces of adhesive (and broken glass, if any) thoroughly from the case before re-sealing your watch. Scour the case using the tip of an opening tool or spudger wrapped in a lint-free cloth or coffee filter, along with a little isopropyl alcohol (90% concentration or greater).

Don't rush this step. Even a small amount of residue can prevent your display from bonding to the case, causing it to come loose over time.