  We provide a method of constructing better-quasi-orders by generalising a
technique for constructing operator algebras that was developed by Pouzet. We
then generalise the notion of $\sigma$-scattered to partial orders, and use our
method to prove that the class of $\sigma$-scattered partial orders is
better-quasi-ordered under embeddability. This generalises theorems of Laver,
Corominas and Thomass\'{e} regarding $\sigma$-scattered linear orders and
trees, countable forests and N-free partial orders respectively. In particular,
a class of countable partial orders is better-quasi-ordered whenever the class
of indecomposable subsets of its members satisfies a natural strengthening of
better-quasi-order.
