Dear
Éric,
i hear you've asked for an SM team built around munchlax, well today is your lucky day!!
Let's start with a basic set. We can fill in the coverage move later.

(click sprites to view)
My biggest concern with munchlax is that it struggles to punish foo, so I feel like adding a ghost just to scare it from clicking hjk. That should make foo easier to play around and potentially help munchlax trade with it if really needed. Opting for frillish to keep things interesting and because it synergises nicely with body slam paras.
We're still gonna need a fight resist though. Don't think mareanie works here at all, it conflicts with frillish. Could try spritz or snub, but I like foongus the most because it covers snivy, gives us a sleep absorber for other foonguses, absorbs tspikes, and is generally a better pokemon imo.
At this point the team is very weak to pawn so we need a fighting type. In this case, foo is preferable to timburr becuase of regen/longevity, which is much needed considering how fat the team is so far. This also makes us incredibly weak to vullaby, leaving no choice but to add an Onix at the same time.

There's some important set choices here. With 4 mons that lose to vull, this team needs all it can get, so Foo is fast with max attack in the hopes of catching out offensive vulls (ohkoes after rocks). Acrobatics helps break foongus as we don't have a great foongus switchin.
Onix needs endure as a way of stopping shellder, and endure means it needs stone edge for compatability reasons. Adamant is important for stone edge rolls vs vull.
For the last slot, the team needs something really fast (20+ speed) and strong, as there isn't much of an offensive presence. There aren't many pokemon that meet this criteria, as most scarfers are underwhelming offensively. The only scarfer I consider threatening enough to make up for it is Rufflet, which kinda sucks without removal, but it's so much scarier than every other scarfer that I think it's worth it anyway.

Now we can fill in Munchlax's last moveslot with EQ as a way to break onix for rufflet.
At this point you might be wondering, "where's the Vullaby?"
And you're absolutely right to question that. A team without vullaby is a waste. So for the final touch, lets delete munchlax and replace it with spdef Vullaby.

This fixes a lot of issues. It provides removal for the rufflet. It's a 2nd knock off user (1 wasn't enough). It gives us a proper Foongus counter, allowing Mienfoo to drop acrobatics and instead run fake out for priority. Having a proper foongus counter also allows us to drop synth for hp fire, fixing the ferro matchup. And it covers the glaring Timburr weakness. All whilst having a better offensive presence than Munchlax.
merry christmas!