you COULD start with some epic sidechains ..
but i wouldnt..
just bc it has a reason: it takes allot power AWAY and id rather just want to have that power to blast me out of my shoes.
thats the only reason i dont use it.
you could just start with some kicks n cymbals to give you a beginning.
and build it with the rest of you cymbals / percs / thingy's.
let the bass come in at around 1 min ..
and let some melody flow into it at around 1:30 ??? just some random ideas ..
and when your done, try to build it .. off, the opposite of building-up, to make a breakdown happen.
Forgive me my Godd*amn english .. it sucks.
but i can atleast hope this wil kinda help you out :)
goodluck with it ^^
Now just make it into a song and I'll give you 10/10 :)