Get a Brewing Stand
Get Blaze Powder
Get Nether Wart
Get Magma Cream
Get Water Bottles
Put Blaze Powder in the Brewing Stand as fuel
Place Water Bottles in the Brewing Stand
Brew Nether Wart into Awkward Potion
Add Magma Cream to the Awkward Potion
Collect the Fire Resistance Potion
Optional: add Redstone to extend the duration
Optional: add Gunpowder to make it a Splash Fire Resistance Potion
Optional: add Dragon’s Breath to make it a Lingering Fire Resistance Potion