Slagolicious

To craft a pressure pot: (glass = g, iron ingot = i, bucket = b, blank space = _)
g i g
i b i
_ i _

To craft a cold slag pot: (stick = s, coal = c, gunpowder = g, pressure pot = p, bottle water = w)
s c s
g p g
s w s

To make a hot slag pot, heat a cold slag pot in a furnace. To use, just right click on gravel, and it - as well as touching gravel - turn to smooth stone.