The manual: "Spiders and insects can nest inside the burner of the appliance and disrupt gas flow. Inspect the burner at least once a year." The method is from the help centre and the Essentials Guide.
Look at the burner at least once a year for webs, nests and food.
Let the oven go cold, turn the gas off, disconnect the regulator and put on gloves.
Blast compressed air over the burner from inside the oven.
Every 3 months, wipe the burner tube with a wire brush to remove food debris (Essentials Guide).
Reconnect, do the leak test, and run it for 30 minutes.
Through the stem: inside the burner
The help centre ("My gas-powered Ooni oven has an uneven flame").
Let the oven go cold, turn the gas off, and disconnect the hose from the gas terminal.
Push the knob in and hold it.
Blast compressed air into the terminal where the hose attaches, so it blows through to the burner.