So to start, you're going to need a glass pan, parchment paper, and Perler beads. The kind that you iron into weird floppy shapes when you're a kid and then lose or maybe use as a coaster or something. BUY THE BRAND NAME BEADS. I will show you at the end what I ended up with when I used beads from Oriental Trading (it's bad).
Preheat your oven to 450. You're melting plastic.
While that is happening, sob softly while you try and get your Perler beads nice and spread out and stood on their ends in the glass dish on some parchment paper. It will take a while, so turn the oven on and by the time you hate handling these beads it should be ready! (Side note: I had to buy Wilton's parchment paper because it was all the grocery store had, but are there other brands? Cheaper brands? I could totally use some money saving tips, that stuff was expensive)
Beep beep beep! The oven is ready so slide these bad boys in and leave them in for "15 minutes." I put it in quotes because I'm pretty sure my altitude and gas stove make it necessary to leave them in for more like 30, but when I learned how to do this, they said 15 so start there and if it needs more, be patient. You may not get a perfect batch every time (as you can see in my picture) but the ones that work are really nice and look cool for way cheaper than buying them at the craft store.
So I also wanted to share a photo of my horrible first experience. This is what happened with the cheap beads (which when I say "cheap" I mean I found them and used them vs buying them. Perler beads are super cheap anyway). You can see that they not only didn't form "dots" they just look like sad donuts, they weren't round, and some of them discolored and look gross.
You can see from the color of the parchment paper that I even put them back in a little longer to try and get a better result but those holes just wouldn't close. They were really nice colors at the start too but somehow this happened. The Perler beads were definitely the better choice here.