  In this work, we give a new technique for constructing self-dual codes over
commutative Frobenius rings using $\lambda$-circulant matrices. The new
construction was derived as a modification of the well-known four circulant
construction of self-dual codes. Applying this technique together with the
building-up construction, we construct singly-even binary self-dual codes of
lengths 56, 58, 64, 80 and 92 that were not known in the literature before.
Singly-even self-dual codes of length 80 with $\beta\in\{2,4,5,6,8\}$ in their
weight enumerators are constructed for the first time in the literature.
