Arrange 12 2-ounce plastic cups (without lids) on a baking sheet. Set aside.
Add the jello and boiling water to a 4+ cup measuring cup or medium mixing bowl with a spout. Whisk until the jello dissolves completely.
Whisk in the tequila, cold water, orange liqueur, and lime juice.
Pour the jello mixture into the plastic cups, filling them about 3/4 full each. Refrigerate for 2-3 hours until the jello is set.
When you're ready to serve, run a lime wedge around the rim of one of the plastic cups and then dip the rim into margarita salt or granulated sugar. Garnish with a lime wedge and/or a strawberry and they're good to go. *Skip this step if you'll be taking the shots to a party or not serving them immediately, instead pop the lid on each cup.
Notes
Store any extra shots in the fridge with the lids on the cups for up to 1 week.
If you want to give these shots more of a kick, swap out the 1/4 cup of cold water for an extra 1/4 cup of tequila.
I recommend silver tequila. Gold tequila can slightly change the color of the shots, but if that's all you have on hand it's 100% fine to use gold tequila instead of silver.