With my old employer, the HSA was a part of the Medical Insurance. It went into our HSA accounts tax-free, which is a heck of a deal & savings. The only problem we had was if you didn't spend it all that year, you lost what was left. We had to calculate/estimate our costs in advance. If you have long-term, yearly costs, it is easier. With dentists, it was easier if you had, say, kids about to go into or in orthodontry to straighten out teeth. You dentist could give you pretty acurent estimates.
There were so many complaints, the policy got changed so you didn't lose the money, but that was years ago, so who know, now. Tax policy keeps changing, and never for the better for the non-rich. Since HSAs are still around, that's hopeful. Check whoever handles Health Insurance at you employer, which may or may not be HR.