A different approach is required to size workshops involving large deliverables for a long running programme.
The most important thing is to make it multi-disciplinary to bring in people from all the capabilities that would be involved in delivering the work.
Using sticky notes, folks would add their thoughts to discrete sections and discuss, rationalise and tidy them up.
Align on a shared understanding to focus the rest of the workshop and define the measures of success to know the problem is solved.
Leaning heavily on Section 3, start to pull in the things we’ll need to do to and putting it in a logical order or flow tends to help.
Start with t-shirt sizes and build up more clarity as things progress, then take a bit of a leap get the group’s honest view of how big or small the tasks are.
Use ranges of estimates where possible and consider how confident we are in our final overall estimates.
Agree on a short succinct justification statement for why the confidence level is what it is.
This approach was fruitful overall in helping to deliver consistency in large programme with many teams, dependencies, and governance requirements.
Consensus building, honesty, continuous learning, and respect are key to successful workshop sizing.