Since there is comparatively lack of standardisation at Business/Op Model design, consulting firms have their own toolbox and approaches (i.e. TOM Playbook, Bank-on-a-page etc.)
You can check out the book 'Business Model Generation' by Osterwalder. Although it is not industry standard, it provides a nice framework to approach Op Model design at a high level. Other methodologies I've seen approach aspects/layers of OM more individually and at more detailed level.
There is also TOGAF, which is originated from IT and aimed more towards Enterprise Architecture side. One of its layers was 'Business Architecture' and as far as I know, due to increased popularity, they were trying to buff up this part in future versions.