I hadn't seen the laisee vouchers before. They did a really nice job with the template. Made a few via their telegram bot (you can also download the template and use your own lnbits) and they came out very nice.

rijndael

bitcoin

Various methods for gifting bitcoin where funds for unclaimed gift are returned 

cointastical

Great list! 

You could also make a new wallet in whatever software you want, write some directions in how to the seed into bluewallet or something and sweep to a new wallet, and just keep a copy of the seed phrase. Put on the directions that itll “expire” whenever and then just sweep the funds if they don’t claim them. 

Edit: i saw brad said “without explaining how to set up a wallet” but i think having some easy to follow, self contained directions is actually a decent solution if you’re trying to make it asynchronous 