Two 10 × 11 cm cards — macOS shortcuts for either side of a 15″ MacBook trackpad.
Print & cut
Print on A4, landscape. In the print dialog set Scale = 100% (not “Fit to page”) and turn Margins → None/Default — this keeps the cards at exactly 10 × 11 cm.
Cut along the dashed borders.
Slide card 1 under the keyboard on the left of the trackpad, card 2 on the right.