Where does Demise expect me to fight him

There's been new light shed on this, by Nintendo itself in the form of a Zelda artbook.

Source: Kotaku

Bokoblins are actually not too difficult to fight, they're not very smart if you know how to attack them.

When fighting them, just keep alternating between left and right horizontal strikes, maybe throw in a Spin Attack or two. Don't stop if they block, just keep swinging. It takes at most 3 hits to knock them down and possibly a Fatal Blow to kill them off. Just beware when in groups, you might have to dodge backward immediately after knocking one down or you might get hit from one of the others.

The thing is, they will only block in a certain direction and hold that direction for a second or two. So if you swing from the right and they block, they should be open on the left and that's where you hit them. In groups, it might be tricky since you might be hitting one but another one will block and you might not connect with the second hit, just dodge back just in case.

Later in the game, you'll encounter Electric Bokoblins which nullifies this tactic. With these guys, a block means a shock to you so you'll have to use more conventional tactics. These really work with almost any enemy in general. If one approach doesn't work, try the next.

Perhaps the easiest way to deal with them would be to use a Skyward Strike on them. As long as you swing it in their direction, it will always connect and knock them down giving you an opportunity to deal the Finishing Blow.

The next thing to try would be to use the Shield Bash when they attack so that you can counter. You will want to have the Sacred Shield (or better) in this case that way you won't get electrocuted (and you wouldn't want the Wooden Shield at this point in the game).

Alternatively if you want to be the aggressor, this can be somewhat difficult to pull off due to the awkwardness of the motions. Choose a direction (left or right) to point the tip of your WiiMote to while moving the rest of your arm in the other direction. This should draw their guard to the side you are pointing. This is where you can swing your arm in the direction pointed to (or flick your wrist) to perform an "opposite" attack.

As a last resort, you'll have to bite the bullet and dodge their attacks and counter. Use your best judgement there on which directions to dodge. Overhead attacks could be dodged left, right or back. Attacks from the right should be dodged moving left or back. And reverse that for attacks from the left.