In a small bowl, mix together the oregano, sesame seeds, cumin, and pepper flakes until evenly incorporated. Set aside.
Heat a grill over medium heat. When heated, spray the grates liberally with the non-stick spray.
Thread a piece of salmon onto a skewer, pushing down until it's about an inch or two from the end. Next, thread on a slice of lemon that's folded in half. Repeat until there's only an inch or two left on the other end of the skewer, ending with a piece of fish. Repeat until all the skewers are filled, or all the ingredients are used.
Lightly spray the kebabs with non stick cooking spray. Salt & pepper both sides. Season the skewers liberally with the spice mixture on both sides.
Grill the fish, turning periodically to prevent sticking, about 8-10 minutes or until it's opaque and flaky.
Eat immediately off the skewer, or serve with cooked basmati rice and roasted asparagus for a complete meal.