Raised beds on or in the mulch? – Reddit Post

I’m pulling up sod in my yard and planning on building a garden area similar to this one. I am pulling up 3in of sod, laying down cardboard/newspaper, and then filling it with 3in of mulch. Is there any wisdom as to whether it is better to put the raised bed on top of the cardboard and fill 3in of mulch around it, or spread the mulch first and place the raised bed on top? I’m thinking raised bed on top is easier because I can do the project in stages, but I’m worried about settling as the mulch decomposes. I’m also worried about excessive rotting on the raised beds if they are in direct contact with soil and surrounded by mulch. Thoughts?