Mix flours, salt, and thyme in a large bowl. Mix liquids into the flour with a fork just until the liquid is absorbed and large clumps are created. Knead lightly 4-5 times forming the dough into a ball.
In a small bowl mix vegan mayo with grainy mustard and 1 teaspoon of thyme. Slice tomatoes into thick slices and remove the seeds and excess juice from them.