Cut the ripe avocado in half, remove the pit, and scoop the flesh into a medium bowl. Squeeze the lemon juice over the avocado and season with kosher salt and ground black pepper to taste. Mash everything together using a fork until the mixture is mostly smooth with a bit of texture remaining. I like to leave it a little chunky for extra bite.

Arrange the cucumber slices on a serving platter. Using a fork or small spoon, gently dollop some of the prepared avocado mixture (from Step 1) onto each cucumber round, spreading it evenly.

In another medium bowl, combine the lump crab meat, mayonnaise, Sriracha sauce, and finely sliced green onions. Season the mixture with kosher salt and ground black pepper to taste, then gently stir everything together with a fork so the crab meat remains in nice chunks.

Place a small scoop of the spicy crab mixture (from Step 3) on top of the avocado-topped cucumber rounds (from Step 2). Sprinkle with sesame seeds and extra sliced green onions for garnish. I like to go a little heavy on the sesame seeds for a satisfying crunch and nutty flavor.

Transfer the assembled cucumber crab bites to a serving platter. Serve immediately with a small dish of soy sauce for dipping.