Combine tamari, rice vinegar, brown sugar, sesame oil, sriracha, garlic, and ginger in a water tight container.
Slice mushrooms to about 1/3 inch thick pieces. Marinade for about 8 hours in the tamari mixture, tossing to re-coat occasionally. Note: the mushrooms will release some of their liquid into the marinade, so you will see the volume of the marinade increase as it sits.
Place mushroom slices on a dehydrator try, and dehydrate at 125 F for about 12 hours (use more of less time for thicker or thinner slices).