I wouldn't really advise this, mainly because Water and Ice are very frequently special moves. They're also two very common offensive types as well, and with Landorus being x4 weak to Ice, it's not really going to be taking hits too well.
>0 SpA Clefable Ice Beam vs. 252 HP / 252 SpD Landorus-T: 224-268 (58.6 - 70.1%) -- guaranteed 2HKO
>252 SpA Keldeo Hydro Pump vs. 252 HP / 252 SpD Landorus-T: 326-386 (85.3 - 101%) -- 6.3% chance to OHKO
>252 SpA Manaphy Ice Beam vs. 252 HP / 252 SpD Landorus-T: 300-356 (78.5 - 93.1%) -- guaranteed 2HKO
>252 SpA Mega Manectric Hidden Power Ice vs. 252 HP / 252 SpD Landorus-T: 248-292 (64.9 - 76.4%) -- guaranteed 2HKO
Landorus also has mediocre sp. defence, and while it also has mediocre defence, at the very least its ability will help give it a buffer. It does learn Calm Mind, but you need to use a turn to set up, while Intimidate activates upon switch in.
So, having said all of that...
Landorus @ Leftovers
Ability: Sand Force
EVs: 252 HP, 170 Sp. Def, 86 Def
- Calm Mind
- Sleep Talk/ HP Ice
- Earth Power
That's the best I can come up with. If you want Calm Mind on Landorus, it really needs to stay in and stall.
It might be better to use Landorus on a Sand team, with Hippowdon/ T-Tar so it can make use of Sand Force at the very least.
Realistically, a Calm Landorus isn't suited to competitive battling.