In a medium bowl, combine oats, ground flaxseed, and salt. Give it a quick toss to distribute evenly.
In a separate bowl, mix peanut butter, honey, and vanilla. If stiff, microwave for 10–15 seconds to loosen. You want a stirrable, glossy mixture.
Pour the peanut butter mixture over the dry ingredients. Stir with a sturdy spatula until every oat looks coated. It should be thick—not crumbly, not runny.
Add mini chocolate chips, coconut, and your festive mix-ins. If the dough seems dry, add milk or water 1 teaspoon at a time until it holds when pressed.
Pop the bowl in the fridge for 15 minutes. This firms the mixture so rolling is a breeze (and keeps chocolate chips from melting into your hands).
Scoop 1 tablespoon portions and roll into balls, about 1–1.25 inches. Expect ~18–22 bites depending on your scoop size and “taste tests.”
Roll some in extra coconut or festive sprinkles for presentation points. Santa's got standards.
Place bites on a parchment-lined plate and chill 10 minutes more. Then transfer to an airtight container.