Clarity and ease of interaction are critical for mobile devices that users rely on daily. As smartphone use time rises, manufacturers are exploring e-paper displays for their advantages, including longer battery life and reduced eye strain. Yet, e-paper technology comes with inherent design limitations, such as reduced responsiveness, constrained color ranges, and ghosting. To address these limitations, we present the first version of our E-Paper Design System comprising a set of design components and guidelines developed specifically for e-paper smartphones, with a particular focus on minimalist devices. The E-Paper Design System is released as a free, open resource on Zeroheight and documented in the Appendix for reference. Our design decisions are grounded in technical constraints, prior research and insights from designers and developers using this pilot version of the design system to create custom mobile applications. We also report findings from an exploratory in-house UX study (N=24) testing developed applications, highlight remaining e-paper-specific design challenges and outline future research directions.