You can boil the proscribed amount of irish moss for 10 minutes, let it cool a bit (but definitely not enough for it to gel) and pour it in. It will form a layer about 3/8" thick on top of the liquid. After about two days, it will start making "threads" off the bottom of the layer, which will eventually fall to the bottom once the sequester enough proteins. Sometimes right at the beginning, they get all clumped up and just stay stuck on the top, so after about a day or two if you see the "threads" you can gently "knock" on the carboy (as if it were a door), and the ones that are ready to drop out will do so.
IM/whirlfloc does need to be boiled, but I can't think of any reason why it absolutely has to be boiled with the wort (definitely no functional reason, I would assume). Adding it later results in that gel layer, but it drops out after a few days and is functionally equivalent to doing things the normal way.
Primary: star thistle traditional mead
Secondary: mango melomel, Biere de Garde, dark strong braggot, oud bruin, Paulaner clone, coffee RIS
Bottled: rye wit, sticke alt, Graetzer, Apfelwein, zeus SMaSH, APA