I do not think there is a unique methodology; if there is I have some explaining to do as to the reason my workbooks appear so different to those of others.
Some of the experts on this site appear to have an amazing repertoire of tried and tested formula approaches at their finger tips. I do not.
I start by analysing the input data and naming the larger objects to capture their relationship to the business problem. As Ali suggests, different problems might lead one to consider array formulas, pivot tables, PowerQuery or VBA. I then try to identify a sequence of process steps (merges, lookups & joins, filters, sorting, aggregation …) that will, step by step, generate information from which the solution should emerge.
Only then do I start writing formulas to generate these intermediate data objects, which I either try to place in a business context or hide away if they are a mere computational device that lacks business significance.
Finally, the solution is packaged, tested, documented and delivered.