The default plinth joiner piece for the IKEA METOD system was tiny and easily knocked off while vacuuming and eventually lost and does not cover gaps.
Designed a new piece using the joiner nubs for the original plinth end cap pieces and added a covering piece to hide badly sawn/worn off edges of the plinth pieces
Print with supports everywhere with the plinth covering piece or the largest flat side facing down as shown in the attached images.
Use bobstro's support settings for best results:
Printed in PETG at 0.20 mm layer height. Feel free to test with PLA.
The author hasn't provided the model origin yet.