Disclosed herein is an impression tray to be removably attached to an oral jaw advancement appliance that is worn over the teeth of a user during sleep to reduce the effects of snoring and sleep apnea. The impression tray has a handle with a first end affixed to a curved rear impression forming stop and an opposite free end that is pushed through the oral appliance so as to extend outwardly from the front thereof. The curved rear impression forming stop of the handle is held flush against the rear of the appliance, and a curved front impression forming stop is detachably connected to the opposite free end of the handle and slidable therealong to lie flush against the front of the appliance. The handle of the impression tray permits the oral appliance to be lowered into and lifted out of boiled water so that an accurate impression of the user's teeth can be made therein.