Start by mixing them together with a spoon or spatula, and then use your hands to finish kneading the mixture until it starts to clump, make sure all of the dry ingredients get incorporated.
Scoop the mixture into 1-ounce portions (about the size of a packed tablespoon) and roll each portion into a smooth ball between your palms. Transfer to a zip-top bag or container to store.
If stored properly in an airtight bag or container, these protein balls should keep well in the refrigerator for 2 weeks, or in the freezer for 3-4 months.