We cut out a smaller-than-finished doorway in the thermal layer of our oven today. The weather has been cold and wet, so the clay hasn't firmed up fully yet. As a result we thought it best not to start removing the bulk of the sand just yet.
Still, it looks more like an oven now, which is nice. And so far nothing has sagged, for which I'm very grateful.
We'll eventually cut this door wide enough to fit the 14" pizzas we like to make. Right now it's only about 12" at the inside edge. There will be a wooden cedar door to insert in the opening once the fire has been removed and the food is baking.