Oak slabs are half version of their respected blocks. They occupy either the top half or the bottom half of a block, or both.
To make Oak Slab, you will need Oak Wood Log and Oak Wood Planks. Please follow the following steps to make an Oak Slab.
Oak Wood Log
In order to make an oak slab, the item you will need is wood Log of oak tree. Find an oak tree and use your iron axe to chop down a wood log. You can find oak trees in the Forest Biome.
Oak Wood Planks
After that you will need to use the crafting table to craft wood planks. Go towards the crafting table and open up 3*3 crafting grid to add oak wood blocks in the center or any cell of the grid. You will get oak wood planks in the right-side box of the crafting table. Add these wood planks into “ready to use” stock. Planks can be used for building structures, as crafting ingredients, and as fuel.
Now use the crafting table once more and simply add three oak planks in any row of the crafting grid. You will get oak slabs in the right-side box of the crafting table. Add these slabs in your “ready to use” stock.