Brew an Awkward Potion using a Water Bottle and Nether Wart
Add a Glistering Melon Slice to the Awkward Potion to make a Potion of Healing
Use Glowstone Dust to upgrade it to a Potion of Healing II
Use Gunpowder to turn it into a Splash Potion of Healing
Use Dragon’s Breath on a Splash Potion of Healing to make a Lingering Potion of Healing
Place the required items in a Brewing Stand with Blaze Powder as fuel