We have accumulated enough measuring spoons (typically from garage sales) to dedicate them for specific purposes, which means keeping them from wandering away:
The design is simple enough:
The slot is a rounded rectangle about 2 mm larger than the spoon handle in both directions, inside a rounded rectangle large enough to put the handle just clear of the jar. The curved side comes from outsetting the jar lid OD by a millimeter (for the double-sided foam tape), then subtracting that circle from the holder.
So, yeah, they’re custom-made for the spoon and jar in hand.
They come from a sheet of 1/4 inch = 6.3 mm Vintage Acrylic. The holder on the smaller jar is two stuck together with super-whoopie low-surface-energy tape before being stuck to the lid. I’m trying the tape on some non-critical projects to see how it behaves: so far, so good.