According to dadiOH :
It isn't all that great for your purpose. The dowels, that is,
because you'll be screwing into their end grain. If you could insert
the dowels from the desk edge they would work fine.

The dowel idea is pretty good, but I'd use cross-grain _plugs_,
not dowels. You can buy such plugs from most hardware stores.

Another idea is to buy/make some thin strips (say, 1/2") of wood,
and bore for T-nuts, install T-nuts, then glue and screw the
strips as "battens" to the underside of the platform, and fasten the
thing being installed to the T-nuts.

Or, instead of T-nuts, just glue and screw the strips.

Or, use knockdown threaded barrel nuts. They have a bolt thread
on the inside, and a particle board thread on the outside. Bore
the appropriate hole, then screw the "nut" into it (usually an
allen key). Much stuff is built like this (ie: Ikea knock-down
furniture). Many places carry these things - like Home Depot,
Lee Valley or Woodcraft. Sometimes you can buy them as repair
parts from Ikea.

Particle board screws generally come in 2" lengths, designed to go
through a particle board sheet into the "end grain" of particle
board (eg: making boxes and cabinet carcases or hanging shelves).
You won't find particle boards short enough for the OP's purpose.

I do the screw and glue thing. Most of the time you need a bit of
a standoff to clear the lip of the counter anyway.

Fastening things to particle board is often difficult. Either
screws/glue and LOTS of surface area, or purpose-built fasteners
(like T-nuts or the aforesaid barrel nuts).
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.