Preheat your oven to 400°F (200°C) and line a small baking sheet with parchment paper.
Toss the sliced zucchini and red bell peppers with olive oil, sea salt, and black pepper on the prepared sheet.
Roast the vegetables for 15-18 minutes until they are tender and show light golden edges.
While the vegetables roast, heat a non-stick skillet over medium-high heat and sear the seitan slices for 2-3 minutes per side until browned.
Toast the sprouted grain bread slices until they reach your desired level of crispness.
Spread the hummus evenly across one side of each bread slice and sprinkle the nutritional yeast over the hummus.
Stack the seitan, roasted zucchini, and roasted peppers onto one slice, then top with the fresh baby spinach.
Place the second slice of bread on top, press down firmly to secure the layers, and slice diagonally to serve.