To make a nether wart block, you will need Nether Wart and then have to use the Crafting Table. Please follow the following steps to make Nether Wart Block.
In order to make nether wart, the basic item that you will have to find and get is nether wart. For that you have to enter into the nether to find a nether wart. Go and find nether wart in nether fortress. You need to explore the nether fortress to get at least nine nether wart.
Nether Wart Block
Now you have to use the crafting table to make a nether wart block. Head towards the crafting table to add nine nether warts in 3*3 crafting grid to get a nether wart block in the right-side box of the crafting table. Add this block in your ready to use stock. The Nether wart block is used for decorations.