The best-practice artifact for expressing a product strategy is a written narrative — modeled on Amazon's six-pager — rather than a slide deck or a bullet-point roadmap. The narrative format forces the author to lay out the data and logic for why a given problem is the most important one to solve right now, satisfying the transparency ingredient of Three Ingredients of Good Strategy: Focus, Transparency, Bet.
Prose narrative resists the temptation to state conclusions without showing reasoning — a slide of bullet points can hide the absence of analysis, while a six-page narrative cannot. This makes it a practical antidote to the "wishful thinking" failure mode.