To make clay in Little Alchemy 2, the most straightforward way is to follow this sequence of combinations starting from the basic elements:

1. Combine earth + water to make mud.
2. Combine earth + fire to make lava.
3. Combine air + lava to make stone.
4. Finally, combine mud + stone to create clay.

Additionally, there are several other possible recipes for clay including combinations like mud + sand, stone + liquid, mineral + rock, and more, but the mud + stone method is the fastest for new players.