Whisk flour, oats, ground flax seed, cinnamon, and salt together in a bowl; add peanut butter and honey and mix until thoroughly combined. Shape mixture into teaspoon-size balls.
Pour about 1/2 the sesame seeds into a large frying pan and cook over low heat, stirring or shaking the pan every minute until fragrant and toasted, 3 to 5 minutes.
Transfer toasted seeds to a bowl and toast remaining sesame seeds.
Spread toasted seeds into a wide, shallow bowl.
Roll peanut butter balls in the toasted sesame seeds to evenly coat.
