Here is the seller's advice:
Hi Pete
Yes, for supporting the MyrtleMat I recommend a set of our substantial Myrtlewood Iso Blox (2.6"x1.6"x1"). Better by far than the cheap rubber/cork numbers you sometimes see in this application (which are simply re-branded compressor feet from the HVAC industry.)
A set of our large Iso Blox is $21.
For what it's worth, maple butcher block does not insulate as well, or have the tonal quality of either solid single-piece maple or our proprietary myrtlewood platform (which is assembled from stock.) And generally, the same mass of myrtle will outperform maple in absorbing unwanted vibration and resonances. Myrtle's grain structure is that much more complex and diffuse. For comparison: even when using solid, single-piece maple, it can take a thickness of up to 6 inches to equal the sonic benefit you'll get with the 1 1/2 inch-thick MyrtleMat.
Best, Dan