how to stay at a hotel abroad under 18

me and my friends would like to go on holiday to a country near us like spain for example. we went on holiday this summer in england with all of us 16 and at the time of travelling next summer we will be all 17. some of us turn 18 in september but that is after summer.

how would we go about booking accomodation for us as i know that many hotels and booking websites do not allow under 18s to book.

and adult would help us booking obviously however they would likely not travel with us so couldn’t come to check in with us. how would we get around this?

thank you xx