How does stamp collecting work these days? Since stamps are printed on pressure-sensitive adhesive paper, how do stamps get put into a stamp collection?

Way back, 100 years ago, I collected stamps – in fact I still have my stamp collection from the 1960s and 1970s, which is probably worth something, but who knows?

Anyway, in those days I bought single stamps and mounted them with those stamp hinges. But I could mount them one at a time and for a kid of 10–12 years, that’s all I could afford.

For the last 15 years, the USPS has distributed stamps that are pressure sensitive and don’t need to be licked. Sure you can buy a sheet of stamps (12, 16,18,20 stamps to a sheet), but as far as I can tell, they don’t sell single stamps at all.

How would a kid collect stamps these days?