Mine cobbled deepslate from deepslate blocks
Smelt cobbled deepslate in a furnace, blast furnace, or smoker to get deepslate
Open a stonecutter or crafting table
Place 4 deepslate blocks in a 2×2 crafting grid to craft 4 deepslate tiles
Or use a stonecutter to convert deepslate into deepslate tiles more efficiently
Use deepslate tiles to craft deepslate tile slabs and stairs if needed