Hi,
presumably I am too late, or disorganized.
How does the Ikea lady come up with the idea that 15cm must remain all around? Normally the rule of thumb is that there should be at least 5cm to the next cutout on the right and left, and 10cm to the outer edge or joint. I think the saleswoman just wanted to be on the safe side since cutouts that close together should/can only be done by professionals. Solid wood panels from Ikea are generally also a bit tricky, as they are not made from one piece but from many glued wooden pieces, except for the Akerby. Because of the different wood structures, it is even harder to get a decent, straight cut. In that case, the 5cm webbing between the cutouts is already quite daring.
If you want to have the panels cut by a joiner, which I find extremely reasonable, you should have this done on-site, so he can take measurements himself and install the panel right away. If this is not possible and you have to go to the joinery with the panels, then as a tip, have the cutouts only SCORED. At most 2cm deep, and do the rest yourself at home. A fully cut-out countertop is quite unstable and breaks very quickly.
Best regards
Nayla