Grind the sunflower seeds into a powder in your food processor. Optionally, instead of doing all the chopping, you could throw the veggies in the food processor after the sunflower seeds are ground up to save time.
Put ground/chopped veggies and seeds in a large mixing bowl and add the flax meal. Add half the water and work the mixture with your hands. Add more water if the mixture is too crumbly. Add more flax meal if it gets too watery.
Dehydrate burgers for 6 hours on a lined dehydrator sheet at 105 degrees. Flip burgers and dehydrate until desired texture is achieved. Serve on Whole Wheat Onion Bagels, or use that recipe to make buns (bagels with no hole).
With "the works" - Put the burger on the bottom half of the bun, then spread mashed avocado on top. Add a slice of onion, a slice of tomato, and 1-2 lettuce leaves, then top of bun.