What some people do, is epoxy seal the whole thing onces it's finished, but then you're committing to that look and it'll take a lot of sanding to change it. It also means all the different pieces of wood can't expand/contract on their own. But then you get that perfectly smooth easy to clean surface. I've never done it, but plenty of YouTube videos show the process.

What Id recommend, is just paying attention now to if crumbs/dust/whatever get stuck there. And filling those places.

If a quick wipe cleans out the cracks, not a big deal.

If theyre deep enough to trap stuff, then yeah, you'd want to fill it to make future cleaning easy. Or keep a dustbuster handy. Like that corner with a triangle missing, crud will get stuck there and it's going to always be dirty.

But anything youd want to fill, now is the time. That way it can be filled, sanded level, and stained with everything else. It should all blend in this way, and not really be noticable.