How do I remove my iMac's stand?

The last iMacs with detachable stands were the 2011 models.

iMac (Late 2012 and later): VESA mount compatibility - Apple Support

If you have a newer model, you need a hacksaw.

Current iMacs can be ordered ready for a VESA mount

Buy 24-inch iMac with Built-in VESA Mount Adapter - Apple

but you cannot remove the stand from a standard "footed" model newer than 2011.

There are some VESA-type mount that attach to the stand with removing it. Example ( not a recommendation)

https://www.amazon.com/VIVO-Adapter-Designed-Monitors-Mount-MACM1/dp/B09MV1L7SH/ref=sr_1_2?crid=21WE66RSJWE62&dib=eyJ2IjoiMSJ9.QFrMerz1jsXzgrsfNwva7rLT_2l9idoMPZ4bHtO0BqLFfRmeku3Q51TPGeGfQzZKO5-Ir2CUlIeAAHuj9CSh8gVqxAGN-MA8DdTjJFnqLOE3ciDCr1UGP0BGRegWmRlr47MMNoF-H0Ln0mepmxRtKMfY-e1PCkTls5RJE351VyV0e5LZ8Q81fn4cTueRQ__LewQhsNGnpzlBU8O_1y4G3w4203LTBBBUhBMSPKtzin4.UbMXT80Jyy0yOLXkOUnX_AA6Z0OZ87kgTKhqU2flLQY&dib_tag=se&keywords=imac+vesa+mount&qid=1708716275&sprefix=imac+ves%2Caps%2C284&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

If your iMac is 2009-2011, let us know and we can find instructions.

No, they are not removable. If you are looking to VESA mount an iMac that needs to be done when you place the order with Apple. You can order iMacs with VESA mounts pre-installed but you cannot do it after the fact.