Best method to clear large sections of land to bedrock

This is very difficult, because water and lava source blocks are unaffected by TNT, so any underground veins would become a problem unless you're willing to put in the time commitment to go around with a bucket and collect each and every single source block. I wouldn't be surprised if you are (I would be), so really, just place TNT on the land you want to clear and blow it up. Simple as that. Also, try to be systematic about it. I know from experience that systematic work gets the best results (both in Minecraft and in life!).

I would keep placing TNT blocks every 7 blocks or so in a grid formation, lighting them up, watching the fireworks, then placing TNT blocks again in the same locations.

• The deeper you can get them, the better. TNT has a random spherical blast radius.
• You could also randomly place blocks and I suppose it would save time. You could go deep and create a huge cluster of TNT underground, then blow it up.

Of course you get get a bunch of friends and clear the area manually (Or even do it yourself.) Have fun!

What I would do:

Make a tower out of blocks (I would say 10 high but the height is not crucial).

Place a dispenser facing down on top of the tower.

Load the dispenser up with TNT

Make this redstone circuit:

Then complete the circuit!