Heat a large cast iron pan or heavy-bottomed skillet until it’s very hot. Toss the snap peas with the olive oil in a medium bowl, and season with kosher salt and black pepper. Working in two batches, add half of the snap peas and cook, tossing often until charred in some spots, about 3 minutes. Remove the first batch, let the pan heat up again and then cook the second batch of peas. As an alternative, use your grill and heat to medium-high. Set a wire rack or grill basket on the grill grate and grill peas on the rack turning occasionally until lightly charred, about 4 minutes. Repeat with the remaining peas. Toss the snap peas with the lemon zest, lemon juice, flaky salt, red pepper flakes, and the fresh herbs. Season to taste. Serve warm.