  We continue the study of classical and quantum low-density parity check
(LDPC) codes from a physical perspective. We focus on constructive approaches
and formulate a general framework for systematically constructing codes with
various features on generic Euclidean and non-Euclidean graphs. These codes can
serve as fixed-point limits for phases of matter. To build our machinery, we
unpack various product constructions from the coding literature in terms of
physical principles such as symmetries and redundancies, introduce a new cubic
product, and combine these products with the ideas of gauging and Higgsing
introduced in Part I. We illustrate the usefulness of this approach in finite
Euclidean dimensions by showing that using the one-dimensional Ising model as a
starting point, we can systematically produce a very large zoo of classical and
quantum phases of matter, including type I and type II fractons and SPT phases
with generalized symmetries. We also use the balanced product to construct new
Euclidean models, including one with topological order enriched by translation
symmetry, and another exotic fracton model whose excitations are formed by
combining those of a fractal spin liquid with those of a toric code, resulting
in exotic mobility constraints. Moving beyond Euclidean models, we give a
review of existing constructions of good qLDPC codes and classical locally
testable codes and elaborate on the relationship between quantum code distance
and classical energy barriers, discussed in Part I, from the perspective of
product constructions.
