Bomb Strat is a technique that saves roughly 10 seconds in the first DHC cannon room, to get the first key of the dungeon. It consists of using a bomb to reflect two cannon shots while you sword slash the other two shots, this skips having to create clones.
There is no perfect way of performing this and runners are recommended to feel out the best method for themselves, however the main parts will be explained.
Entering the cannon room on the far leftwith sword and bombs equipped.
Place and then pick up a bomb at a consistent position
Move around the first fence up to a specific spot on the floor then throw the bomb upwards (dodging the canonballs)
Roll right and then head to the 2 right cannons, sword slash the shots as they are fired
If everything was done correctly then all the canons die and a short cutscene plays, if its failed then you have to activate the ezlo trigger to the left before creating clones to solve the puzzle the intended method.
Enter the room on the far left with bombs and sword equipped.
Walk up above the entrance blocks to place and immediately pick up a bomb. Start holding Up + Left until you reach the first barrier, then hold Up until you pass it, at which point you can then hold Up + Right, then just Up once you're inside the green column.
Stop at the blue row (align yourself with the eye on the left wall) to throw the bomb then start holding Right to then roll right.
After the roll you can either do the roll up technique or the walk up technique (cf: TGH) :
Roll up : After the roll, walk right so that you won't be blocked by the second barrier when rolling up, roll Up, then align yourself in the second column and start slashing when in range of the cannons, without being too close.
Walk up : During the roll, start holding Up + Right, then just Up when passing the barrier, then Up + Left after crossing the barrier, then just Up when inside the second column. Slash the cannonballs when in range.