How to build an XP farm from a spawner in Minecraft
On the side where you will stand, put a Stone Brick Slab in the top half of the block at the mobs' feet (layer 3), and a full block under it.

The Stone Brick Slab is classic gray stone bricks cut into a slab. Its material is Stone Bricks, so it keeps that block's look and toughness. All slabs, stairs and walls work alike, as the Stone Slab, Stone Stairs and Cobblestone Wall pages explain; the Stone Bricks page covers the material.
It is made with the Crafting Table from 3 × Stone Bricks (other recipes also exist). It is mined with a pickaxe.
3 × Stone Bricks → 6 × Stone Brick Slab
// Slots with several items cycle through every accepted option.
On the side where you will stand, put a Stone Brick Slab in the top half of the block at the mobs' feet (layer 3), and a full block under it.
Lay Stone Bricks and put a Chiseled Stone Bricks block (2 Stone Brick Slabs on top of each other) every 4 blocks in both directions, like the joints of large tiles.
Stone Brick Slab, Birch Planks
| type | top · bottom · double |
|---|---|
| waterlogged | true · false |
At the Crafting Table: 3 × Stone Bricks give 6 × Stone Brick Slab. At the Stonecutter: 1 × Stone Bricks gives 2 × Stone Brick Slab. Mining the block drops it.
It is a building shape of Stone Bricks, used for floors, roofs, steps and low walls. It is an ingredient in one recipe: Chiseled Stone Bricks.
The fastest tool is the pickaxe.
No difference: the Stonecutter turns 1 × Stone Bricks into 2 × Stone Brick Slab, the same rate as the crafting recipe (3 × Stone Bricks for 6).
Placed under a Note Block, Stone Brick Slab gives the Bass drum sound.