In HCI and design research, it has recently been suggested that, instead of risks and threats, uncertainties can be generative resources. This aligns particularly well with practice-based design research and research through design (RtD), where uncertainties are pervasive and unavoidable due to the approach's interest in open-ended problems, contexts under transformation, and unknown futures. Building on the idea that uncertainties drive design activity, we describe the design process as framing acts where a designer-researcher moves along perceived uncertainties. We identify three dynamics for a generative mode of working with uncertainties that can make designers aware of uncertainties, circle in towards those that appear essential while seeking to avoid others, and stay with those that offer new perspectives. We exemplify these dynamics by drawing from our experiences from three RtD projects and highlight this viewpoint's value in providing new reflective tools for designer-researchers.