Prep the base. In a large bowl, combine oats, ground flaxseed, chia seeds (if using), and salt. Stir to distribute the dry ingredients evenly.
Mix the “glue.” In a separate bowl, whisk peanut butter, honey, and vanilla until smooth and glossy. If your nut butter is stiff, warm it 10–15 seconds in the microwave to loosen it up.
Combine. Pour the wet mixture over the dry. Use a sturdy spatula (or clean hands) to work it together until no dry pockets remain. If it's crumbly, add milk 1 tablespoon at a time until cohesive.
Add the fun. Fold in mini chocolate chips and any optional add-ins. Keep the chips last so they don't melt into the warm nut butter, unless you want a chocolate swirl—your call.
Chill briefly. Pop the bowl in the fridge for 10–15 minutes. This firms the mixture and makes rolling a breeze.
Roll. Scoop about 1 heaping tablespoon per ball and roll between your palms into 1-inch balls. Aim for uniform size so they set evenly and look pro.
Set and store. Place on a parchment-lined tray. Chill 20 minutes to firm up, then transfer to an airtight container.
Serve. Enjoy cold for maximum chew, or room temp for a softer bite. Either way: dangerously snackable.