Explain the solution strategy as compact as possible (e.g. as list of keywords)
Explain your solution strategy in keywords, e.g. as a short list of relevant decisions or approaches.
You explain the details as a concept in arc42 section 8 (crosscutting concepts).
You should emphasize on creating an overview, less on completeness or detailed explanations.
See also tip 4-2 (solution strategy as table).