Add the water, red pepper, onion, tomato and mushrooms to the blender and blend until smooth.
Add the almonds and sunflower seeds and blend again until no large lumps remain.
Mix in sesame seeds and ground seeds then pour the mixture onto a silicone sheet or similar on a dehydrator tray and spread to approx 1/2 - 2/3 inch depth.
Dehydrate at approx 100F for 3 hours or until the top feels dry to the touch.
Place a second dehydrator tray over the top. Flip the other way up then carefully peel off the silicone sheet. Continue dehydrating for approx 3 hours more.
Cut up with scissors then fill your sandwich.
I added avocado, carrot ribbons, yellow pepper, and cucumber to mine.