I like to use cooking analogies, e.g. imagine saying "we'll make the pizza gluten free later". It's theoretically possible you just have to carefully detach the toppings, cheese and tomato sauce from the crust, and move them onto a new gluten-free crust. But it's a LOT more effort.
Haha, I think the analogy actually works better because the second pizza will almost certainly still carry the risk of being a terrible experience. Because gluten is a protein, it would likely still be on all the swapped toppings, proving building it in at the start is always a better idea!
Oh yeah, hadn't even thought about it that way, just that the resulting de-glutenified pizza would be quite a mess structurally.