Slabs to blocks - reuse slabs you no longer need

Smelting sand in blast furnaces - smelting Sand and Red Sand into Glass in Blast Furnace

Cooked Carrots - Normal Carrots, but you eat them twice as fast

Craft 6 stairs instead of 4 - crafting stairs in a crafting table will yield the same amount of stairs as if you were using a stonecutter

Use Blackstone and Endstone to craft stone tools

Nether Wart Blocks to Nether Warts

Blasting Netherrack into Nether Bricks

Blasting Raw Metal Blocks into Blocks - smelt Raw Iron, Copper and Gold blocks in a Blast Furnace

Blasting Clay - smelt Clay Blocks into Terracotta Blocks and Clay Balls into Bricks in a Blast Furnace

Blasting Cobblestone - smelt Cobblestone into Stone and Cobbled Deepslate into Deepslate in a Blast Furnace