The most important thing to note about this set is that the playstyle and set remain the same whether you choose to go physically or specially defensive; Lickitung just ends up walling different Pokemon depending on whichever you choose. Specially defensive is the most common choice and arguably a better way to use Lickitung due to the fact that it has no special weaknesses, and physical walls are far easier to come by in the tier. With a specially defensive spread, Lickitung is one of the few Pokemon that can avoid a 2HKO from Huntail's Surf in the rain, allowing it to stall out rain turns and paralyze or poison Huntail in return. Wish and Protect provide Lickitung with reliable recovery, and it is one of the few Pokemon in the tier with access to Wish, giving it a major leg-up on its main competition in Kecleon.
Lickitung's main niche in the tier is that it is able to run both Wish and Heal Bell on one set, allowing it to function as a kind of one-stop-shop for stall teams looking to compress roles in one team slot. Heal Bell is pretty invaluable for stall teams in NU, as a lot of stallbreakers rely on Toxic to break through some of the main defensive Pokemon in the tier, most notably Sableye and Flareon, but also other defensive Pokemon like Relicanth and Tropius. Alternatively, and also somewhat ironically, Toxic is probably the best way Lickitung is going to spread damage on the opponent's team and allows it to outstall Pokemon like Flareon with the combination of Wish and Protect. So, if you have Heal Bell covered elsewhere on your team, likely by Chimecho, Toxic is typically going to be the best choice for the third slot. Seismic Toss is the main option in the last slot to spread consistent damage on the opponent's team due to Lickitung's abysmal attacking stats and allow it to prevent Pokemon from using it as complete setup bait, particularly Substitute users. Alternatively, Body Slam can be used, since it still does a decent amount of damage to frailer special attackers like Plusle and can paralyze foes if that's desired for your team.
If you already have a special wall on your team, Lickitung can play around with its defensive EVs to better suit your team's needs. A fully physically defensive spread can be used by moving the Special Defense EVs to Defense and changing the nature to Impish. With a physically defensive spread, Lickitung can actually outstall a lot of the physical attackers in the tier not named Hitmonchan, notably Choice Band Sudowoodo (avoiding Focus Punch and Explosion), Kingler, Flareon, and Murkrow. Lickitung can also run a more balanced EV spread of 252 HP / 88 Def / 168 SpD with a Careful nature, which can allow it to take on a broad range of unboosted threats in the tier. With that spread, Lickitung has just enough physical bulk to avoid the 2HKO from Choice Band Murkrow's Drill Peck and enough Special Defense to avoid the 2HKO from Bellossom's Solar Beam.
Lickitung's movepool is absolutely gigantic, so there's lots of room to play around with its last two slots; feel free to fill them in with whatever best suits your team. One thing to note is that Lickitung's Special Attack is actually higher than its Attack, so its special movepool options aren't out of the question. The most prominent alternative is Shadow Ball, which allows Lickitung to actually touch Haunter, something it can't do with the given set. Knock Off can be used somewhere on the set to help its team win stall wars, as Pokemon like Sableye become significantly easier to 2HKO without their Leftovers recovery, and Choice Band threats like Hitmonchan are significantly easier to wall without their item. As for special attacking options, Ice Beam, Flamethrower, Thunderbolt, and Hidden Power Grass all have their uses and allow Lickitung to better combat certain threats like Tangela, Huntail, and Pupitar should your team need it.
Regardless of the EV spread chosen for this set, Hitmonchan remains a major threat, as it can easily OHKO Lickitung with Sky Uppercut, even if Lickitung is running a fully physically defensive spread. Chimecho, Haunter, Swalot, or Pelipper is a required teammate if using Lickitung to assuage this issue. Physically defensive Pokemon like Pelipper and Relicanth love Lickitung as a teammate, as Lickitung can wall nearly every Electric-, Grass-, and Water-type attacker in the tier effectively, giving them a solid backbone to fall back on and pivot around, and Lickitung can pass them Wishes because they lack solid recovery of their own. Unfortunately for Lickitung, Rain Dance Huntail can 2HKO it with Hydro Pump, even with a fully specially defensive EV spread, but Lickitung can effectively stall it out if it hits Huntail with Toxic as it uses Rain Dance and continues to cycle with Wish and Protect. This should be a last resort strategy for dealing with Huntail when using a stall team, however, so a primary answer is needed, making specially defensive Bellossom a desired teammate.
If using a physically defensive spread, a specially defensive teammate like Swalot or Whiscash is recommended; Swalot in particular can still wall Hitmonchan effectively if it's running a specially defensive EV spread. Spikes support makes this set much more effective, as Lickitung can force out a lot of Pokemon and, combined with Toxic, really build up passive damage. Roselia is the best in this regard, as it resists Fighting unlike Cacturne and Glalie, and it is the best fit for the kinds of stall teams you would be using Lickitung on.