Simple, yet effective, XY calibration template.
Correct your slicer`s dimensions settings until all similar elements fit well.
Dimensions are:

• plates 25x25 mm, 2 mm tall;
• thick ledges/slots 5x10mm;
• thin ledges/slots 2x8 mm;
• large holes/cylinders 7 mm;
• small holes/cylinders 3 mm.
  PLA, 0,15-0.2 mm, any infill.