Recently there has been extensive coverage of Under Speaker Isolation in the Linked Thread.
https://forum.audiogon.com/discussions/footers-under-new-speakers
If the footers in the Link are purchased to create a quantity of 12 Items, as a Set of 3 x Footers per tier, and used in conjunction with tiers made from Densified Wood Board, there is not much out there to improve on things at the purchase price.
An added bonus being the items purchased, 616 and if the board is bought direct and produced at a dimension suitable for other roles, i.e, a TT Plinth, will sell at another time with a full remuneration of the original outlay, the reality being a appreciated value when sold on.
It is the road less travelled, but those who do this from the current Products in the Market Place are paying substantially more for what amounts to very little as a difference.
https://www.fromjapan.co.jp/japan/en/auction/yahoo/input/t1192434588/