If you are using wooden skewers, soak them in water for at least 20 minutes to prevent them from burning. Preheat your grill to medium-high heat, roughly 400°F (200°C). Clean the grill grates and lightly oil them to prevent the shrimp from sticking.
In a large mixing bowl, whisk together the olive oil, lemon juice, sea salt, black pepper, and red pepper flakes. Add the cleaned shrimp and the cut garlic scapes to the bowl. Toss everything gently until the shrimp and scapes are evenly coated with the marinade. Let them sit for about 5 to 10 minutes while the grill finishes heating.
Thread the ingredients onto the skewers, alternating between a piece of garlic scape and a shrimp. For the scapes, it is best to pierce them through the center of their curve so they stay secure. Ensure the shrimp are pierced through both the tail and the head end so they do not spin when you flip the skewers.
Place the skewers on the hot grill. Cook for 3 to 4 minutes on the first side. Use tongs to carefully flip the skewers over and cook for another 2 to 3 minutes. The shrimp should be opaque and pink, and the garlic scapes should have light char marks and be slightly tender.
Remove the skewers from the grill and place them on a serving platter. Squeeze fresh lemon juice over the top while they are still hot to brighten the flavors. Serve immediately while warm.