Typically, a corporate culture assessment involves the following steps:
Data & document analysis - Numbers don't lie, so taking a look at the facts and figures can highlight areas of concern when it comes to the health of your internal culture. Some key areas to look at include employee wellbeing measures, KPIs around staff turnover, sickness absence as well as your strategy documentation, website, values, leadership behaviours and so on
Interviews - Interviews allow you to get a first-hand insight into your organisation's culture from the people affected.
Workplace culture assessments - we use the cultural transformation tools from Barrett Values centre for this www.valuescentre.com
Team Psychological Safety assessments  - we use the Four Stages of Psychological Safety model from www.leaderdfactor.com for these