Measurement of the time-resolved or "slice" transverse properties of the electron beam is fundamental for X-ray free-electron lasers like SwissFEL. Multiple-quadrupole-magnet scans are the standard approach to measure the slice emittance and optics. This talk introduces a new method for measuring the slice beam parameters utilizing a single-quadrupole-magnet scan. Besides scanning less magnets, the approach is more intuitive, generally requires smaller magnet strengths, and allows designing the measurement set-up in a convenient way. We present simulated and experimental results at the SwissFEL injectdor that show the validity of the method.