  We show that geometric frustration in a broad class of deformable and
naturally curved, shell-like colloidal particles gives rise to self-limiting
assembly of finite-sized stacks that far exceed particle dimensions. When
inter-particle adhesions favor conformal stacking, particle shape requires {\it
curvature focussing} in the stack, leading to a super-extensive accumulation of
bending costs that ultimately limit the ground-state stack size to a finite
value. Using a combination of continuum theory and particle-based simulation,
we demonstrate that the self-limiting stack size is controlled by the ratio of
the intra-particle bending costs to inter-particle adhesion energy, ultimately
achieving assembly sizes that are tuned from a few, up to several tens of,
particles. We show that the range of self-limiting assembly is delimited by the
two structural modes of "frustration escape" which evade the thermodynamic
costs of curvature focussing. Crucially, each of these modes can be suppressed
through suitable choice of adhesive range and lateral patchiness of adhesion,
providing feasible strategies to program finite assembly size via the interplay
between shape-frustration, binding and deformability of colloidal building
blocks.
