so you mean the MC can't just conjure himself some porridge sand (grinded oatmeal), drown it with milk sand (milk powder) mixed with water, then eat it with a baked grain sand (toast) and wet fruit sand (jam) while drinking tea sand (teabags) with water?
Preposterous, next thing you'll say is that you can't make clothes out of sand.
considering this series' nonsense thus far (just 10 chapters in!), i'm honestly surprised that sand-clothes hasn't happened yet. since something made entirely out of loose particles and bound by invisible, frictionless, weight-nullifying forces is gonna be however flexible you want it to be, all it'd take is a particularly fine grain suspended "
just so" to prevent chafing and you'd have a shockingly sturdy and comfortable suit to wear. i mean, he's already made beds and shit, right? if the sheets are somehow insulating enough, don't feel like (literal) sandpaper, and are truly otherwise as comfortable as the characters act like they are, then clothes seem downright practical.
...also much less brain-hurting than all of the shields and whatnot he's conjured, since at that point the sand technically doesn't contribute
any structural support at all aside from visible surface area for incoming attacks to hit before the magic does 100% all of the work in transferring all of the energy from the strike elsewhere in order to keep the sand in place. it's like your standard invisible fantasy shield spell but with extra steps, the only possible benefit i can even imagine is just formulating the spell to work solely on sand- no need to contribute mana/casting time/whatever in order to make the spell able to interact with any kind of metal or wooden (or other) weapon material that hits it- but that point is kinda (extremely) moot since his "sand magic" is now explicitly shown to interact with basically every kind of metal and mineral (and maybe even wood, at least if it's petrified?) as long as it's dry & in particulate form...
ultimately, this series is really just the bog-standard isekai fantasy format but with a different coat of paint. MC is removed from his home where he's ordinary and powerless, finds himself in a place where he suddenly has the ability to create/do anything he pleases, he can do no wrong, every woman he meets is thirsty for him, etc, etc... the only technical difference is that instead of creation magic or whatever that lets him summon anything from thin air, there are a couple of "restrictions" like water, but since he nonetheless instantly finds enough of it to create a lake in the middle of a Sahara-esque desert, it seems like the author is desperately clutching onto said technicalities to get away with being the JP equivalent of a Soundcloud rapper without the shame of being labeled as such lol. "no guys, it's not an isekai, i swear! he's a native and has always had those abilities, it's totally different!"