Bake the vegan "fish" fingers in the oven according to the instructions on the packet.
Meanwhile, slice the avocado or smash guacamole-style with the back of a fork and season with lemon, salt and pepper.
When the "fish" fingers have just a couple of minutes left, add the burger buns into the oven to warm through.
Time to assemble! Layer up the bottom burger bun with half the vegan mayo, vegan "fish" fingers, avocado, leafy salad and Midsommer sea salad. Tentatively balance the top bun on top, repeat for the second sandwich and enjoy!