Bring a large pot of salted water to a rolling boil. Add the gnocchi and cook according to package instructions until they float to the surface, usually 2 to 3 minutes. Use a slotted spoon to remove them and let them drain thoroughly on a clean kitchen towel. Pat them dry if needed. This step is critical because any moisture will prevent the gnocchi from crisping properly.

Heat the olive oil in a 12-inch frying pan over medium-high heat until it shimmers, about 2 minutes. Test by adding one gnocchi - it should sizzle immediately. Add the remaining drained gnocchi in a single layer without overcrowding. Cook undisturbed for 2 to 3 minutes until they develop a golden-brown crust on one side.

Gently stir the gnocchi using a wooden spoon and continue cooking for another 2 to 3 minutes, allowing them to crisp on multiple sides until golden and slightly firm to the touch.

Reduce the heat to medium and add the minced garlic, stirring constantly for about 1 minute until fragrant. Watch carefully to prevent burning.

Add the fresh spinach to the pan, stirring gently until it wilts completely, about 1 to 2 minutes. Season with salt, black pepper, and red pepper flakes if using. Remove from heat and stir in the crumbled feta cheese. Serve immediately while hot.