I think every company has its own tricks for storing bitcoins and they will keep them secret for security reasons. But if we imagine, I think companies will store bitcoins in hardware wallets that use multiple signatures. Company officials will each have their own key and they will have to come together to open the company wallet

As far as I know, hardware wallets are the safest wallets and ensure that the computer device must be completely clean when used for transactions, maybe the company also has a special computer that is only used for transactions so that the wallet is completely safe from malicious attacks