Our kitchen drawer has a molded insert.  I hate to see good knives being abused, so I designed a small parameterized horizontal knife block.  

In the customizer, “flat width” and “flat length” refer to bottom flat surface of the molded cubby.  These dimensions are VERY difficult to measure.  I suggest you get creative with your slicer to print only a slice of the knife block in both directions to test your fit.  Only then print the whole thing.