Cut your tempeh into bit sized pieces (about ½ inch thick), grate/finely chop your ginger, and mince your garlic.
Whisk ginger, garlic, tamari, maple syrup sesame oil, and rice vinegar together to create marinade. Pour marinade over tempeh pieces in a medium bowl, ensuring full coverage. Allow to marinate for at least 30 minutes and up to 1 hour.
Heat avocado oil over medium heat in a cast iron or non-stick pan. Remove tempeh from marinade and arrange in the pan in a single layer. Allow to sear, approximately 4-5 minutes per side.
Once tempeh is seared on both sides, add the marinade into the pan with the tempeh and allow to come to a very light simmer. While marinade heats, create a slurry with your arrowroot powder. Mix powder with ~1 Tbsp water and mix well to combine.
Once marinade reaches a simmer, add the slurry and mix to combine. Allow to cook for another 2-3 minutes. The arrow root slurry should thicken your marinade to create a sauce, at which point, remove the tempeh and sauce from the pan. Serve immediately over rice, zoodles, or eat alone--optional: garnish with sesame seeds!