Set a sturdy work table or platform just in front of the oven and pad the surface of the table with a towel or cardboard to protect the table.
Open the oven door and remove the mounting screws that secure the oven to the sides of the oven cabinet. Slide the oven forward in the cabinet. You should have enough slack in the electrical conduit of the power supply; if not disconnect the power supply wiring from the junction box for the wall oven.
With someone's help, carefully lift the oven out of the cabinet and set it on the table in front of the cabinet.
Tip: Use the installation manual for your wall oven to guide you in this step.