How to get, grow and ride a Happy Ghast in Minecraft
Put 3 Leather on the top row, then Glass, Wool, Glass on the middle row.

Leather comes from animals: Cows, mooshrooms, horses, donkeys, mules, llamas and hoglins drop up to two pieces each. It is needed for books, item frames and bundles, for leather armor and for the harness of the happy ghast.
It is made with the Crafting Table from 4 × Rabbit Hide.
Leather armor is the lightest armor in the game and the only one you can dye: combine a piece with any dye to change its color, and mix several dyes for custom shades. It protects little, but it is cheap and it is also the armor that keeps powder snow from freezing you.
Most of your leather ends up in other items. A Book needs three paper and one leather, which makes leather the bottleneck of enchanting bookshelves. An Item Frame uses one surrounded by sticks, a Bundle one with a string, and a harness needs three, with two glass blocks and a wool block, to ride a Happy Ghast.
Without cattle nearby, four Rabbit Hides combine into one leather. A novice Leatherworker buys it for emeralds, and leather armor can be repaired with leather on an anvil.
4 × Rabbit Hide → Leather
// Slots with several items cycle through every accepted option.
Put 3 Leather on the top row, then Glass, Wool, Glass on the middle row.
Craft one from 3 Leather and 1 Iron Ingot, or find one in chests:
3 Paper and 1 Leather.
Craft a Saddle from 3 Leather and 1 Iron Ingot, then use it on the nautilus, or sneak and use the nautilus to open its inventory and drop the Saddle in the saddle slot.
At the Crafting Table: 4 × Rabbit Hide give 1 × Leather. It can be found as loot in Bastion Remnant, Desert Pyramid, Abandoned Camp, Village and 3 more. It is dropped by Cow, Donkey, Hoglin, Horse and 4 more. Bought by Villager: Leatherworker (Novice). Bartering: Piglin. Hero of the Village gift: Villager. Fishing: Fishing Rod.
It makes leather armor, books, item frames, bundles, harnesses and leather horse armor. It is an ingredient in 25 recipes, made at the Crafting Table; for example Brown Harness, Bundle, Cyan Harness, Gray Harness, Green Harness and 17 more.