Sorry to disappoint, but foongus is unbeatable
As stated in the OP, lures are
specific pokemon that run an unexpected move or moveset in order to weaken or directly OHKO a specific threat, and pave the way for another sweeper
Now, the issue with this for Foongus is that you absolutely have to OHKO Foongus from the get-go, or KO it with a combination of a normal attack followed by an unorthodox move. Given the above definition, 2HKOs where only the unorthodox move is used wouldn't be enough for Foongus, as it could merely switch out and heal back a good portion of the damage, allowing it to continue to check whatever else that doesn't have a special coverage move. For example, say you're using LO Ice Beam Shellos to lure Foongus so that your Wailmer can sweep. Foongus is no longer able to check your amazing new Shellos variant, so on paper this is a lure, but since the goal of this thread is
to improve the Teambuilding aspect LC has currently
it isn't an effective lure, because it's completely useless for an actual team as a Foongus lure; you can Ice Beam the Foongus, but if it just switches out, it'll still be healthy enough to check Wailmer, and even if it isn't, it could just switch in and out on something weaker later in the match until Wailmer can't hope to break past it.
So going back to OHKOing/surprise comboing Foongus, the former isn't feasible for a lure because Foongus is bulky enough that arbitrary coverage moves won't be enough, and if you could OHKO Foongus with anything, then Foongus probably wouldn't be switching in.
The problem with surprise combos is that Foongus is a very important mon, so most Pokemon that could run a coverage move to beat Foongus probably will, and this thread is attempting to improve our knowledge of effective lures, so known threats like acrofoo don't count.
Foongus's bulk again comes into play here, because we are now pretty much left with LO + dumb coverage move combinations. In a metagame where Berry Juice is great and Eviolite is better, viable LO mons better have something extra powerful to make themselves worth using. But once Mienfoo or Corphish reveals its LO and gets rid of Foongus's Eviolite, Foongus is already tipped off that it might be wrecked if it stays in, regardless of the dumb coverage move, because:
236 Atk Life Orb Reckless Mienfoo High Jump Kick vs. 124 HP / 160+ Def Foongus: 14-17 (56 - 68%) -- guaranteed 2HKO
(14, 14, 14, 14, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 17)
196+ Atk Life Orb Adaptability Corphish Crabhammer vs. 124 HP / 160+ Def Foongus: 13-16 (52 - 64%) -- guaranteed 2HKO
(13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 16)
196+ Atk Life Orb Corphish Knock Off (97.5 BP) vs. 124 HP / 160+ Def Eviolite Foongus: 8-10 (32 - 40%) -- 99.3% chance to 3HKO
(8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10)
Which is an issue because if Foongus needs to be preserved to check something else, and this is important because the goal of the lure is to get rid of Foongus so that the something else won't be checked, then as soon as it takes a boosted Koff, there's nothing from stopping it from switching right back out.
There may be a very small number of exceptions to the above that are never ever worth using in practice, but overall I feel that Foongus is not a good choice for this thread for the above reasons. As such I suggest that something less cute like houndog should be used, thanks i appreciate it