Making splints is considered basic first aid. A monkey could do it.

Rationale:  When I first made the splint recipes, I had survival (easily acquired) as the primary skill, with first aid secondary.

The difficulty 2 was designed to require survival:2, first aid:1.  Someone shuffled the primary skill to first aid, but did not rebalance the difficulty.

IRL, making splints is considered basic first aid knowledge (something rigid, some wrapping, some tape--easy!)  This recipe should be accessible early in the game.  The game balance remains undiminished, due to the near-realistic healing times required for the splints to heal broken limbs.