Is there a way to see the valid combinations in game? It feels like the worst part of 90s point and click adventures: Trying all the items with each other, in different spots. Except it's even worse than brute forcing as you sometimes need at least a certain amount of items. (Edit: Nvm! Game is good. See below.)
When you hold down left click on a tile, it'll show you all of the recipes for that tile.
When you hold down left click on an item, it will flag the top right of some tiles. The flag indicates that the item is used in a recipe on that tile. It'll be light blue if you've discovered all the items needed for the recipe and dark blue if you still need some. If you hold down right click instead, the game uses the result of the recipe instead.