In Dungeon World, I face a challenge with describing hack-and-slash roll outcomes (particularly on success.) One part of this problem is that I have trouble setting up situations for players to want to do something other than just damage to the foe via Hack-and-Slash. How can I regularly encourage non damage dealing moves via Hack-and-Slash? Additionally, whether they do damage or not, how does one make Hack-and-slash interesting?
You can't "encourage non damage dealing moves via Hack-and-Slash", because Hack & Slash is attacking an enemy in order to damage them.
It's likely players just attempt to Hack & Slash either because they don't know, or have forgotten, that they can (and should) attempt to do anything they please, rather than just "Hack & Slash the goblin" or the slightly better "attack the goblin with my sword".
Try and get the players not to think about "Moves" at all. A player can "attack the goblin with my sword". And a player can push the goblin, cripple the goblin, trip the goblin, grab its arm, grab its leg, slap its cheek, put a bag on its head, dive between its legs (or try to), point past it and yell "Dragon", throw oil over it, throw breakfast over it, ask it for dinner, eat it for dinner... anything. Remind them of this every so often.
We then have to decide what happens when the player says what they're doing. An example: "I'm going to cripple the goblin's leg so it can't move by smashing it with my Mace"
If this were in the midst of combat, the table will likely decide this is "attack[ing] an enemy in melee", so Hack & Slash triggers. The player rolls, hits, and Deals Damage. And when the players look to you to find out what happens as a result of that damage, you may well follow the fiction and make a move which reflects the player's original intent - "Offer[ing] an opportunity without cost", and say something like "The blow shatters the goblin's leg, and it falls to the floor, gasping in pain. What are you going to do?"
If not in the midst of combat - say the goblin is asleep - the table may well decide that no player move triggers at all (there's a good argument for Deal Damage in this case, but I'll ignore that to illustrate the general rule). Whenever anything happens in DW where there's no player move, it is instead a GM move - again, the players looking to you to find out what happens. You may make a move which reflects the player's original intent as above; or maybe have the goblin yell, putting the player in a spot; or reveal the unwelcome truth that the shattered leg is hemorrhaging and the goblin's dying. Something that moves the game along.
Even in the general boring case of a simple Hack & Slash, where the player succeeds and Deals Damage, the GM still has opportunity to move the game along. The player says "I deal 6 damage to the goblin" then (again) looks to you to see what happens. The narration of a Deal Damage is thus a GM move. So narrate the result and immediately follow it up; here revealing an unwelcome truth - "the goblin falls, blood gushing from a severed artery. Sparrow, as it falls, you here an involuntary gasp from behind you, and you turn to see another band that were sneaking toward you from the other side. What do you do?". Use this move to keep the game flowing, and to pass the spotlight around
How can I regularly encourage non-damage-dealing moves via Hack-and-Slash?
Hack and Slash as a move triggers when you attack a character in melee, and its main result is that you deal damage. So, if the character isn't doing anything that would deal damage, it's not the best move to trigger. What triggers instead might be a Defy Danger, or a GM move (remember, not all GM moves are bad for the player characters), or something else.
Your players are going to want to take the route that dispatches the foes as quickly as possible. Ususally, this is by dealing damage. If you want to encourage your players to trigger other moves, make it clear in the fiction that running at them with their sword (or whatever they're currently doing to trigger H&S) isn't going to work, or isn't going to be easy.
Whether they do damage or not, how does one make Hack-and-slash interesting?
I think the question you're trying to ask here (based on your first line) is "Whether the characters are triggering Hack & Slash or other moves in combat, where do I go from there, particularly on a success?"
So the player has got a 10+ and dealt their damage. Let's further assume it didn't kill the enemy. What do you do now? Do what you are required to do at all times as the GM: describe the immediate situation, and make it one that demands a response. Furthermore, you have a little bit of freedom here in that H&S doesn't necessarily only represent one strike, but could be a short exchange until something changes: Enemies rarely stand around taking hits until they die.
It's entirely within your role as the GM to describe what the foe does next. This isn't making a GM move, it's simply describing the immediate situation and the result of the previous move.