Install the current Bambu Studio release from Bambu Lab, then use the configuration wizard to add the Bambu Lab A1 with the nozzle actually installed. A 0.4 mm profile is not interchangeable with a 0.2 or 0.6 mm nozzle profile.
Open a new project and select the physical build plate from the plate menu. The plate choice affects temperature and first-layer behavior, not just the picture on screen. Add the filament preset that matches the material. For a third-party spool, start with the generic preset for that polymer rather than renaming a Bambu preset and assuming identical behavior.
Import a simple model, place it flat and click Slice plate. Spend a minute in Preview. Check the first layer, unsupported islands, total filament changes and the vertical color bar that exposes each toolpath type. If an AMS lite is connected, map every model color to the intended physical slot.
Before sending the job, confirm printer, nozzle, plate and filament one last time. These four selectors are where most avoidable profile mistakes happen. Keep bed leveling enabled unless you have a specific documented reason to skip it.
Save tuned settings as a user preset instead of editing a system preset beyond recognition. Give it a plain name such as Overture PETG A1 0.4. When a print goes wrong, you can compare that preset with the untouched generic baseline.
Getting filament loaded and mapped correctly matters just as much as the slicer profile itself — see the A1 filament loading guide if AMS slots or feeding are not behaving. When Preview shows unsupported islands that need attention, the guide to using and removing supports explains when they are actually necessary. Together those two checks catch most avoidable slicing mistakes before a print starts.