The second step will take the final Slater determinant from the first step (if not empty), and then order by pairwise permutations (i.e., if the Slater determinant is \( i_1, i_2, i_3, \ldots \), then if \( i_n > i_{n+1} \), interchange \( i_n \leftrightarrow i_{n+1} \).