Wait 30 minutes (or follow the instructions on tub) after applying grout and clean the glass pieces with a dry soft brush. (It’s important to clean the glass pieces because once the grout sets, it will be hard to get it off the glass pieces). Once cleaned, let the pot dry for 1 day.
Last thing to do is to put dirt in and place a plant inside. And enjoy.
IKEA FNISS trash can 80 cents, broken stained glass bought for $20 from Amazon, Weldbond adhesive 5 bucks, grout 6 bucks. Total cost under 35 bucks.