Is there a trick to make blast furnace?

just so you know what you're getting - it's twice as fast as a normal furnace but it only does ores, raw iron/gold/copper and old metal tools and armour. no food, no glass, no cobble to stone. it burns fuel twice as fast too, so it's quicker, not cheaper. keep a normal furnace next to it for everything else.

no trick, just smooth stone. furnace in the middle, five iron round the top and sides, three smooth stone along the bottom. smooth stone is the bit people miss - it's stone smelted a second time, so cobble to stone to smooth. stone bricks won't do it.