Den of Flames - Stage 1
Everyone should each grab an item then put two characters at the edge of the platform, and use the gust jar behind them to blow them across over the pit. Retrieve the last hero with the boomerang afterward. Stack three people and use the gust jar to blow out the flames around the treasure chest. That one has some rupees. Board the moving platform and you'll find another chest far to the right; that one has hearts in it. Pick it up if you need it. Continue onward to the gateway.
Den of Flames - Stage 2
Quick one here. Drop down to the lower platform and step on the three switches to call forth a group of Hardhat Beetles. Use the gust jar to blow out their flame shield and then hack them twice with the sword to kill them. Or, the gust jar can also blow them off the platform and kill them instantly.
Den of Flames - Stage 3
Put two characters at the edge of the platform, and use the gust jar behind them to blow them across over the pit. Retrieve the last hero with the boomerang afterward. It's best to stand on the lower edge of the so that it will be easier to avoid the spinning fires on the other side. Board the moving platform and take all the way to the elevator being moved by lava. Use the gust jar to send someone over to the swinging platform, then have the same character push the platform closer to your allies. Push on to the highest point. From here, navigate past the fire traps to the gateway.
Den of Flames - Stage 4
The boss level pits you against more Hardhat Beetles as well as Flaming Keelons. The latter requires a full totem to be blown out and stunned with gust jar. Once the first group is dealt with, another batch will show up and that one needs a stack of two characters to effectively fight off.