Everyone does everything differently. This is what and almost all of my customers and clients do, with crystal clear tanks.
The Fluval pads are made to fit perfectly in their trays so you take them out of the box and put them in. This is simple and easy, but costs a bit more.
Others use filter floss or 100% polyester pillow stuffing and cram it in as tight as it will fit.
Some people don't use any mechanical media besides the foam pads in the outer ring of the baskets.
Some people use Fluval's Biomax biomedia. Others use Eheim's. Others use Seachem Matrix.
Some people don't pay for anything made for aquariums and instead use cheapo alternatives like pot scrubbers and similar things.
Some people will only do the bottom tray as biomedia and fill the middle tray with one or more of the following: carbon, crushed coral, Seachem Purigen, Poly-Filter, peat granules, etc.