Place a steam basket over a large pot with a cup of water and bring to a simmer. Steam the tempeh for 5 minutes, then remove and let cool slightly.
Cut the cooled tempeh into bite size pieces and place in a large bowl with 2 tbsp soy sauce, 2 tbsp corn starch and 1 tbsp vegetable oil.
Preheat oven to 400F. Toss the day old rice with 2 tbsp vegetable oil in a large bowl and spread on a parchment-lined baking sheet.
Bake the rice and tempeh together at 400F for 20-30 minutes, tossing occasionally, until crispy.
In a small pot, combine all teriyaki sauce ingredients (soy sauce, maple syrup, ginger, garlic powder, rice wine vinegar, water and cornstarch) and bring to a boil. Reduce to a simmer until slightly thickened and set aside to cool.
Build your bowl by layering crispy rice on the bottom, topped with crispy tempeh, diced kimchi, cucumber, and green onions. Drizzle with teriyaki sauce and serve.
