I've always just used a plastic pan scraper on our pizza stones, while running cool water on them (after, or couse, the stone is fully cooled). You could always go to the Ooni website to see what their FAQs say.

I would think you could use warm water and a scrub brush. Just, whatever you do, don't use any soap or chemical of any kind.

Can it be soaked?

What is your issue with a plastic scraper on it? That's the instructions on mine. You are to avoid SOAP on it but running hot water across it while scraping is the recommended way. I wouldn't bake the sauce onto it anymore. How difficult this job will be will depend on how seasoned the stone was. Mine is 30 years old and not much sticks to it.

I have a pizza stone cleaning brush.

" What is your issue with a plastic scraper on it? "

Just that I can't quite get everything off......it's not quite flat, and so I'm concerned that it will limit the smoothness of the pizza sliding in and out.

Maybe very gently and carefully scraping with a razor blade?

And alternative to soaking, I'd try leaving a wet sponge or rag over the area to soften it before scraping.

Do you think it would work to run it with no pizza to burn off as much as possible before scraping?

Try baking soda

We leave our pizza stone in the oven when we run the oven cleaner. Works like a charm and returns to almost like new condition.

I purchased one of these scrapers, and boy is it handy. Does everyone have this type of thing?

Anyway, this is the perfect type of thing to do scraping without damaging something.

https://www.amazon.com/gp/product/B00ZKSPM9G/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

The plastic scrapers that I have & use came with various pieces of Pampered Chef stoneware. These scrapers (in brown) available on Amazon are very similar.

I haven’t had a stone in years (have a steel) but I always used a razor blade and as I recall the instructions said to use baking soda.

Just be certain that is completely dry of any absorbed moisture before heating it in the oven (so that the expanding water/steam does not crack the stone).

Food, how do you like the steel?

(and what sort of boat do you sail? I love sailing, but only have small boats — dinghies. I have a few — Sunfish, CL 14 (fave), plastic Walker Bay; O’Day Daysailer.) Nowadays, severe back pain limits my sailining. But I could lose myself for hours sailing close to the water — salt water being my prefered liquid.

Most stoneware is non-porous. It's the earthenware that would be a concern.

Thanks, cindy! So the pizza stone is not porous? Good to know.

The ones I've seen are unglazed, so definitely porous.

Unglazed or glazed. Doesn't matter. It's the type of clay. Former ceramics teacher here for 37 years.

" For robustness and non-porous solutions, stoneware clay provides the ideal materials for such a project. For a less expensive alternative, where durability and robustness is not really a factor, then earthenware is perfect for your project. "

https://www.soulceramics.com/pages/earthenware-stoneware-clay-difference#:~:text=For%20robustness%20and%20non%2Dporous,is%20perfect%20for%20your%20project.

Everything that I was reading about pizza stones and how to clean them, said that they are very porous. I will say that the one I have is very porous. Water will suck right into it.

Perhaps those stones are not stoneware?

From this page:

https://www.epicurious.com/expert-advice/the-best-pizza-stones-and-baking-stones-of-2020-article

"Pizza stones are made of ceramic, cordierite, or a composite material, so they can differ in terms of heat conductivity from model to model. Composite and cordierite pizza stones are more durable and usually a little more expensive than ceramic. Baking steels are, obviously, made of steel, which can be heavier than stone with the same variation in price depending on thickness and brand."

I use a metal dough scraper to clean my pizza stone and never use water.

Here's a discussion on this issue at the Pizza Making Forum.