Craft or place a Brewing Stand
Add Blaze Powder as fuel
Put a Water Bottle in a brewing stand slot
Brew the Water Bottle with Nether Wart to make an Awkward Potion
Add Magma Cream to the Awkward Potion to make a Potion of Fire Resistance
Optional: Add Redstone Dust to extend the duration
Optional: Add Gunpowder to make a Splash Potion of Fire Resistance
Optional: Add Dragon’s Breath to make a Lingering Potion of Fire Resistance
Optional: Use a Fermented Spider Eye to convert it into a Potion of Fire Resistance if needed in certain versions or recipes