How to make banner designs in Minecraft: loom and patterns
put a Shield and the banner in a crafting grid.

The Shield stops attacks that hit you from the front. Held in the off hand, it protects you from arrows, melee hits and explosions, and it can carry the design of a banner.
It is made with the Crafting Table from 6 × Oak Planks (or another variant) and Iron Ingot (other recipes also exist).
Hold the use button to raise it; after a quarter of a second, attacks from the front deal no damage. You walk very slowly while blocking, even slower than when sneaking. Each blocked hit of at least 3 damage costs the Shield some durability.
An axe hit disables the Shield for 5 seconds, whether the axe is held by a player or by a mob such as a Vindicator. Some attacks cannot be blocked at all, such as fall damage or the sonic boom of the Warden.
Combine it with a banner in a crafting grid to paint the banner's pattern on it. Repair it at an Anvil with planks or with another Shield, and enchant it with Unbreaking and Mending.
6 × Any of #wooden_tool_materials + Iron Ingot → Shield
Shield + Any of #banners → Shield
// Slots with several items cycle through every accepted option.
put a Shield and the banner in a crafting grid.
An arrow passes through 4 mobs and ignores shields
Shield (6 Planks and 1 Iron Ingot) and Bucket (3 ingots), to block arrows and carry water.
full armor, a Shield against crossbow bolts, a bow or crossbow, food, and Healing potions if you have them.
At the Crafting Table: 6 × Oak Planks (or another variant) and 1 × Iron Ingot give 1 × Shield. It can be found as loot in Trial Chambers. Sold by Villager: Armorer (Journeyman).
It blocks attacks coming from the front when raised, and it can show a banner's design.
336 durability points: each use removes one, and it breaks when none are left. Mending and Unbreaking can extend it.
No: only one per inventory slot.
3 enchantments: Mending, Unbreaking and Curse of Vanishing.