Rinse the greens thoroughly under cold water, then roughly chop them and set aside.
Prepare your equipment: a large skillet, a wooden spoon or spatula, a small bowl for garlic and lemon, and your knife and chopping board.
Heat the skillet over medium-high heat until hot, then add the olive oil, swirling to coat the bottom of the pan.
Add the minced garlic to the hot oil and cook, stirring constantly, until fragrant—about 30 seconds—until you smell that sweet, pungent aroma and see the garlic turn slightly golden.
Immediately add the greens in batches if necessary, pressing them down with your spatula, and cook, stirring frequently, until they wilt and turn vibrant green—about 2 minutes.
If excess water is released, increase the heat slightly to evaporate it, about 1 minute, until the greens look glossy and tender.
Squeeze the fresh lemon juice over the greens, add a generous pinch of salt, freshly cracked pepper, and chili flakes if using. Stir well to combine and let the flavors meld for about 30 seconds.
Taste the greens and adjust seasoning as needed, aiming for a bright, earthy flavor with a slightly smoky aroma.
Remove the skillet from heat, sprinkle with toasted nuts or seeds if desired, and serve immediately while warm.