How do I land heavy and huge (4m Dia) payloads on Laythe in a controlled manner?

[Selective Genius]

How do I land my heavy modules on Laythe within a small radius, so that it wont be a pain to assemble them?

[AHHans]

Well, you could use a plane/glider - i.e. a craft with enough aerodynamic lift that you can fly it a good distance cross-country - or you do a propulsive landing - i.e. a craft that can traverse a reasonable distance on rocket engine thrust. (Jet engines work on Laythe so that gives you more options.)

My plan is to place my (one-piece) Laythe base with a combination of parachutes and rockets: not much traverse needed for this, just want the ability to fine-tune the place where it goes. And then visit it with SSTO space-planes. (Both are currently in transit to Jool.)

[Zhetaan]

On 3/15/2020 at 9:30 AM, Selective Genius said:

How do I land my heavy modules on Laythe within a small radius, so that it wont be a pain to assemble them?

Carefully.

In seriousness, it is possible to have accurate parachute landings provided that you can slow your reentry to safe deployment speeds consistently and repeatedly.  This is somewhat like booster and pod recovery at the KSC, but it is more somewhat more difficult than Kerbin because Laythe's atmosphere is different enough from Kerbin's that your intuition will be off.  Eve and Duna aren't good trainers, either, because Duna's atmosphere is negligible, and Eve's requires special handling at the best of times.

For practical purposes, you're likely best off with a combination that includes propulsive landing, as @AHHans suggests.

[Mech_Jeb_42]

Use the trajectories mod, if you don't consider that cheating. I'm probably going to cause an uproar in this thread but MechJeb works too. 

https://github.com/neuoy/KSPTrajectories

https://www.curseforge.com/kerbal/ksp-mods/mechjeb

Here are links to both. 

If you are playing on console, your out of luck.