Finish the initial wizard before slicing a custom model. The printer should have passed its loadcell and filament-sensor tests with a clean sheet installed.
Open the current PrusaSlicer, run its configuration wizard and add Original Prusa CORE One with the installed nozzle. Select a standard PLA preset and the physical sheet fitted to the bed. Prusa’s CORE One support page links the current slicer and first-print guidance.
Import a small model with a broad base. Slice it and inspect Preview for a continuous first layer and unsupported islands. Export the generated G-code or BG-code to USB, or send it through the Prusa network workflow you deliberately configured.
Clean fingerprints from a smooth sheet with the method Prusa recommends for that surface. Start the job and watch the first layer through the door. The loadcell sets the nozzle position automatically; do not copy a Live Z procedure from an older Prusa printer unless the CORE One documentation calls for it.
Stop if the nozzle scrapes, the sheet is not pinned flat or a filament blob travels with the toolhead. Otherwise, let the short job finish and wait for the sheet to cool before removal.
Save the project, including its printer, sheet and filament presets. It gives you a known-good baseline for the first larger part.
This assumes the assembled-printer setup in the CORE One setup guide is already finished, since the loadcell and filament-sensor tests need to pass before slicing a custom model. For the general reasoning behind checking a first layer on any printer, see the beginner’s first print checklist, and if a test needs to be rerun afterward, the calibration and self-test guide explains each stage.