You can watch this video from 07:20 if you want to skip on the other parts:
https://www.youtube.com/watch?v=sxty2XhTwVIBasically it's very simple.
You take a currency that requires 21 days for staking/unstaking, then you deposit this amount in Atomic Wallet, stake it and then you can't gamble with the crypto you're holding.
The locking (staking) is done with one single click of a button, and it's practically speaking, equivalent to activation of self-exclusion on an online gambling site with a click of a button (and yet not all sites offer it unfortunately).
For example, you stake (lock) $200 of your crypto, and that's all crypto available for you - then you can't play/gamble/risk it for at least 21 days ... do it 15 times a year time after time, and you would be excluded for a long time.
The only drawback with this method is Atomic doesn't offer this on USDT so some "gamblers" might not like this idea because they trust stablecoins more than other crypto coins, but this is FYI.
Pushing the button to start the staking is where the problem is at, remember that a heart that's filled with the excitement of gambling is already craving to gamble again, it would be different someone else is going to keep pushing that button, but the gambler will still have to make the decision.
I personally do not buy this idea because it depends on the gambler's mind, if he is serious on quitting gambling he or she will do this easily, but if he is the type that has weak mind he won't be able to lock away his money for long, even if he did it once, after the staking period is over he will surely use the fund to gamble.
Like you said, staking is a big problem if you are not using stable coin, because alternative coins are highly volatile, they can lose value so much that when you unstake your whole bag will be worthless, this is the only bad side of staking alts.