Okay, I have a few suggestions...
First, I'll share how I introduced my players, all coming from Pathfinder, to LotFP:
First, we played A Stranger Storm, which is currently available for free in the Referee book:
-This includes a mystery to solve, lots of role playing and NPC interaction, and introduces the "unfairness" of LotFP - there is a 50% chance that a character is lost just by interacting with certain NPCs - but the kicker is, players may not know this until later in the session! There is the added bonus that players are very likely going to fight an exact version of themselves. They will learn first hand how to handle themselves in an exactly evenly matched fight.
Second, we played The Tower of the Stargazer:
-This module feels very much like a traditional dungeon crawl, except it features many LotFP twists. My players learned that they simply cannot save everybody and for the first time in their RPGing careers, actually abandoned their comrades to death. It was a rough but necessary lesson!
Third, we played Better Than Any man:
-This is the whole kit and kaboodle. Players will be required to analyze situations, NPCs, encounters, and monsters. Should we talk are way through this? Fight? Lie? Help them? They must make choices, none of which are "perfect" and then face the consequences of those choices.
Finally, we played The God That Crawls:
-This teaches the players how to manage food and light, that sometimes the monster is simply unbeatable and running is the only option, however, getting as much gold as possible is the only way to level up. They MUST learn how to run, track light and food, and encumbrance, while getting as much loot as possible and hoping to escape with their lives (and XP).
After these four lessons, I think the players were finally suited to LotFP and we've been playing weekly for the last 5 years! I wouldn't do it any differently if I had to do it again.
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Now, if you are intent on creating mini-encounters and not using modules, here's what I'd do for a "balanced" monster encounter:
First, I think the assumption you made about giving the monster(s) the same HD as the players is more or less fair. Just keep in mind that in reality, monsters break all sorts of rules, so this is never a sure thing if you run a pre-made monster.
Second, you can use basically the same stats as the adventurers either combined into one monster or multiple monsters.
Third, give the monster some interesting powers that you know the players can overcome, but will take some puzzling to figure out.
For inspiration, check: Fire on the Velvet Horizon, the monsters in Better Than Any Man, or use one of the Slugs from the free Slugs book and adjust its stats. (It doesn't even have to be a slug, you could just use the stats on a different body...but, honestly, why shouldn't it be a slug!?:)