1. Slice buns and spread each one with a generous layer of hummus. Place on a baking sheet and set aside.
2. Add remaining hummus to a food processor along with drained beans, flour, and cilantro. Pulse until combined.
3. The texture should be paste-like and hold together into a shape to be breaded. Depending on the moisture content of your beans you may need to increase flour to reach this consistency.
4. Place large balls of mixture into breadcrumbs and press down to form flattened balls or full-size patties for sandwiches.
5. Heat olive oil over medium heat until sizzling. Add falafels to olive oil and cook until browned on both sides and heated through (about 4 minutes per side).
6. Toast buns with hummus on them in oven or toaster oven until warm.
7. Assemble sandwiches with falafels, cilantro leaves, tomatoes, cucumbers, and arugula.