Preheat your oven to 200°C and line a baking sheet with parchment paper.
Wash and cut the potatoes into 1.5 cm cubes, then toss them with 1 tsp of olive oil and a pinch of sea salt.
Spread the potatoes on the baking sheet and roast for 25 minutes, turning halfway through, until they are golden and crispy.
While potatoes roast, grate half of the cucumber and squeeze it firmly in a clean kitchen towel to remove all excess water.
In a small bowl, combine the squeezed cucumber, Greek yogurt, one minced garlic clove, lemon juice, and a pinch of salt to create the tzatziki.
Prepare the Greek salad by dicing the remaining cucumber, cherry tomatoes, and red onion, then tossing them with sliced olives and crumbled feta.
Slice the seitan into thin, bite-sized strips and season with the dried oregano and black pepper.
Heat the remaining 1 tsp of olive oil in a non-stick pan over medium-high heat and sauté the seitan with the second minced garlic clove for 6 minutes until browned.
Assemble the bowls by placing a base of roasted potatoes, topping with the seitan strips, the fresh Greek salad, and a large dollop of tzatziki.