In a medium bowl, toss all of the salad ingredients together, minus the feta (it'll make a bit of a mess).
To a blender, add the avocado half, juice from 1 lemon and pinch of salt and pepper. Pulse a few times, until the avocado is broken up. With the blender going, pour in the olive oil until the mixture begins to thicken and become smooth. Add a few tablespoons (I ended up needing about 4 tablespoons) of warm water to help with the smooth texture. I let the blender run for about 1 minute to achieve the super smooth texture. If you're ok with tartness (I think this salad needs it because of the beans) squeeze in the remaining lemon juice and adjust salt and pepper to taste. It may seem too tart right now, but I can assure you that when you toss it with the salad ingredients, it'll be all good.
Add about half of the dressing and lightly toss the salad using your hands or a pair of tongs. Keep adding a bit of dressing as needed
Transfer to a serving plate, if you like, and top with the cubes of feta.