As I know, there is not specific "constitution process" for the strategy Meeting. I set up several strategy meeting using a kind of home made process.
The main idea is :
A - Looking at the company/circle's environment from a very large perspective to a focused one, in order to check paradigm changes, news from the last period, "low voltage" signals, learnings...
B - Setting an agenda from tension sensed through the circle members
C - Processing each tension trough the IDM process in order to set strategic focuses
D - Building the main strategy using the strategic focuses
We detailed all the process in very specific steps, starting by a check-in round and ending by a closing round.
Before that, the LL has to delegate to the circle her/his strategic accountability trough a policy adopted in a governance meeting.