Start by preheating the oven to 400 degrees F. If your green beans aren't trimmed on the ends, then cut off tough ends. You can either keep the green beans whole, or cut them in half.
Line a baking tray with parchment paper. Add the green beans to the tray, drizzle with the avocado oil, and toss. Spread out the green beans and sprinkle generously with kosher salt and pepper. Place the tray into the oven for 20-30 min until the green beans are fork tender and they look somewhat wrinkly. Remove the tray from the oven.
While the green beans are cooking, cut the beets into bite-sized pieces. Then, finely chop the herbs for the dressing (you can use fresh parsley, cilantro, or dill). Next, roughly chop the walnuts.
Make the dressing by adding all the dressing ingredients into a bowl and whisking together. This dressing recipe makes about double the amount you'll need for this recipe. It's a really versatile dressing, so you can use it for other salads.
Once the green beans have cooled down somewhat, you're ready to assemble the salad. Add the greens to a serving bowl (or divide the greens between bowls). Top with the green beans, beets, vegan feta, and walnuts. Drizzle the dressing over top.