Metrics. Or getting it wrong

I was asked to make a cutlery drawer/holder thing for a relative. Two knives, two forks, two spoons. I had some oak left over from a job a few years back to after much pondering I started drawing out solutions, eventually cutting wood. After 4 complete drawers I moved onto the spoons and made a little discovery. I'm aiming for 140mm wide, plus some 4mm oak faced ply sides. Length varying with the eating iron. So off I go and do a few calculations, knowing that the soup spoon is slightly wider than the dessert spoon. I'd ripped some oak to 30x50mm which seemed about right. The spoons were to stand on edge in slots (see the photo below) so as not to be too wide. Previously I'd used a pair of dividers to try and get an even spread of slots. This time the error was too much, my 14mm slot, by the time the error had multiplied over the full length of the piece, was now only 12mm, too slim for the spoon (what do you call the dished part of a spoon?). Restart. I drew it out to scale on paper and pricked it through to the wood. Good enough... except it wasn't. I was practicing on some softwood and realised I'd totally ignored the blade thickness. Fine on the previous drawers where I'd simply moved along by x mm, not in this case where the wood was cut to length. Back to the drawing board. I needed 14mm gap, 8mm separator. Weird, but in the end, I'd a series of 11mm spaced marks (14 - 3mm blade thickness) and the realisation that I had to keep those marks against the right hand side of the blade. When the blade is offset at 15° from the vertical that gets tricky. Made harder by the fact that my drawing was 'side elevation, yet when on the sawtable, it was rotated through 90° towards me. I tried it again on softwood, rotating the saw blade until the tooth that cuts furthest right was level with the table, then aligning that with the mark on my wood. Then I got (a little) smarter, and copied the mark down the table clear of the blade so that I didn't have to switch the saw off between cuts! The first one off the assembly line is shown below.

Needs cutting to length and the 'bottoms' of the slots cleaning out, but the spoons fit, it is regular and I've learned a valuable lesson in metrics.