Customizable knife holder.  Comes apart so you can get inside to clean it out easily in case crumbs or whatnot drop into it. Width of the gaps is a parameter so you can adjust for various knife thicknesses although, in this version, they all have to be the same width so mixing a thick steel knife with a ceramic knife may not be ideal.

This style keeps the cutting edge of the blade from ever touching the holder so you're not dulling your knives just by inserting and removing them.

Designed in OpenSCAD so you can customize most of the parameters.  My first OpenSCAD project so it might not be as dressed up as some but quite functional.

The .stl files are configured for Ceramic knives.

Default tolerances fit the base into the body pretty snugly which is perfect so the thing stays together.

I recommend printing the main body with 3 perimeters, no infill.  This keeps it light but still should be strong enough even in PLA.  It also keeps the fins more flexible.  Print the bottom with significant infill (25%+) to add weight which will keep the center of gravity low to avoid tipping. 

Body should be printed fins down. No supports needed for either piece.

I'd also suggest printing the body and base in different colors for visual interest.  The body in some color to match your other kitchen decor and then black base to anchor it visually would be nice. 

Pictured print is in 3DFuel Standard PLA ReFuel, 0.6mm nozzle at 0.30 layer height, 3 perimeters, 0 infill for body; 3 perimeters, 25% infill for base.

2022-08-24: Version 1.1 of the .scad file now supports wall thicknesses down to 1mm within a reasonable range of radii.