What is the ruling on praying on the foam placed under the carpets in mosques, and what is the meaning of the Hadith: "placing the forehead firmly on the ground," does it mean pressing with it?

Prayer is not valid when prostrating on sponge unless it is compressed such that the forehead is stable upon it. For the obligatory part, it is sufficient to place any part of the forehead with ṭumaʾnīnah (stillness). Tamkīn as-sujūd (firm prostration) means pressing the forehead firmly against the ground, and it is mustaḥabb (recommended). This is done by pressing the forehead on the place of prostration such that if there were cotton underneath, it would be compressed.