Deal 25 cards face down Opening layoutin a 5x5 square, then turn the next card face up and place it at the centre, as illustrated. (Here it happens to be diamondJ.) Use the remainder to deal a hand of 13 cards to each player.
To add cards to the grid in a spiral direction in such a way as to form and score for combinations based on those of Cribbage, namely pairs, prials (three of a kind), double pair royals (four of a kind), sequences of three or more, and (with some restrictions) flushes of three or more. There is no score for fifteens or thirty-one, unless you really want to make it complicated. With scores being made as you go along, it may help to use a Cribbage board.
Each plays in turn, starting with the non-dealer, who plays a card face up to the right of the starter. The next card must be placed immediately below this, the next to its left, and so on, until the spiral is complete at top right, leaving you each with one card unused. (The purpose of this is to give you a choice of two on your last turn.)
The rules are available on Parlett's website here: https://www.parlettgames.uk/oricards/snailspace.html