Please note that the dimensions of lumber are taken before they are planed for smoothness, so actual width and height dimensions are smaller than what is shown on the label.
Sequence is important. Some holes are drilled before gluing, some are drilled after gluing.
There are plenty of plastic drawer-insert tool holders for the automotive industry tool chests, but none suited me. They either didn’t make good use of limited drawer space, or didn’t correspond well with the tool combinations I use in gunsmithing, or the price/value didn’t excite me.I had built a number of oak shelves for my man-cave, and a decade later they were no longer suiting me. So I took them down. What to do with a bunch of oak shelves? I re-purposed them as drawer inserts for my tool chests. Various arrangements accommodated the different heights and configurations I needed.
The basic construction principle was to hold the plank in the mill, and cut so as to leave about 1/8″ at the bottom. Using a ball end-mill on the divider edges and the more-narrow slots, reduces the stress (compared to square edges and corners.