  The relaxation of atomic positions to their optimal structural arrangement is
crucial for understanding the emergence of new physical behavior in long scale
superstructures in twisted bilayers of two-dimensional materials. The amount of
deviation from a rigid moir\'e structure will depend on the elastic properties
of the constituent monolayers which for the twisted bilayer - the more flexible
the monolayers are, the lower the energy required to deform the layers to
maximize the areas with an energetically optimal interlayer arrangement of
atoms. We investigate this atomic reconstruction for twisted bilayers of highly
flexible InSe. Results using two methods are demonstrated - first we train a
machine-learned interatomic potential (MLIP) to enable fully atomistic
relaxations of small-twist-angle large-length-scale moir\'e supercells while
retaining density functional theory (DFT) level accuracy. We find substantial
out-of-plane corrugation and in-plane domain formation for a wide range of
twist angles and moir\'e length scales. We then adapt an existing continuum
approach and show that it can reproduce some, but not all, features of the
fully atomistic calculations.
