Preheat oven to 450°F.
In a bowl, mix the ground chicken with salt, garlic powder, and onion powder until just combined.
On parchment, press into a thin rectangle large enough to match your bun layout. I like to do about a quarter inch larger than the buns so there is some over hang.
Lightly dust with flour, brush with egg, then coat fully in panko, pressing gently to adhere.
Spray generously with avocado oil until fully coated. Flip and repeat on the other side.
Transfer to a sheet pan and bake for 15 minutes, then broil for a few minutes until golden and crispy. Every broiler is different, so keep an eye on it! Mine takes 5 minutes but it can be done in 1-2 minutes if you have a strong broiler.