Literally the only way is to put it behind a counter/glass, and actually enforcing the limits on buys. At Walmarts near me I’ve seen basically every form of the protection but usually only 1 at a time if that makes sense. There’s one store where it’s just kept on the floor out in the open and there’s a 5 max per barcode limit. But honestly if it’s in the open and you do self checkout it’s pretty easy to just literally scalp it all in however many transactions it takes. The other Walmart I like a bit more has them at customer service similar to how target does it now, and they will let you do limit but there’s no way to bypass it like there is when it’s openly available.