Bring a 4-quart / 3.8 L pot of water to a boil over high heat. Add the soba noodles and cook for 4 to 5 minutes, stirring once, until just tender but still a little chewy.

Add the frozen edamame to the pot for the last 2 minutes of cooking to thaw and warm through.

Drain the noodles and edamame in a fine-mesh strainer, then rinse under cold water for 30 seconds to stop the cooking and wash off the starchy coating. Set aside to drain fully.

Whisk the soy sauce, sesame oil, rice vinegar, lime juice, maple syrup, garlic, and ginger together in a small bowl until smooth. Add the chili flakes if using.

Add the cooled noodles and edamame to a large mixing bowl with the cucumber, carrot, and half the scallions.

Pour half the dressing over the noodles and toss gently with tongs or two forks, coating every strand.

Divide the noodle mixture among four bowls. Top each with sliced avocado.

Drizzle the remaining dressing over the avocado and noodles. Scatter the toasted sesame seeds and remaining scallions on top. Serve right away or chilled.