Despite many past efforts to develop haptic experiences of virtual clay modeling, natural interaction with virtual clay remains a hard challenge. In this work, we propose a computational solution for the interactive simulation of clay-like materials with unprecedented realism, coupled with free-air tactile rendering that provides a natural tangible experience. Our solution includes a novel particle-based model of viscoplasticity for efficient interactive simulation, and an optimization-based ultrasound rendering algorithm that takes as input the interaction forces between a virtual hand model and the clay-like material. We demonstrate the effectiveness of our method through expressive creative experiences.