Strategy | World 1 - Zone 3: Fight with King Toad GW2: Super Adventure Box Guide

Between attacks, hit the crystal on Kings neck, it will drop Jewel Shards. As soon as the king begins his tongue attack (turns his head from side to side) pick up the shard and throw it in Kings open mouth, a moment after that you can attack him dealing normal damage. If you have Slingshot and don't really care about using Baubles as ammo attacking with Slingshot will speed whole fight up due to fast attacks.

You just have to avoid the attacks and throw the Shards in the King's open and the boss fight will be over quickly. If it's the first time you beat King Toad as a reward you will get fourth heart.