We sell a set of very good quality spikes for $24, but I also made a pair for myself.
Way back when I did a first floor I had drywall screws, but as JD pointed out they have very little resistance against lateral forces, and they would bend a bit. Of course once a DW screw has a bend, it takes very little to make it fold completely. Although I never took a tumble, it was pretty clear that a nasty fall was a possibility.
So I made V2.0. The wood is 3/4 inch, and ended up using 1/4" lag screw, 1.125" in length. Counter sunk for the lag heads, and just used 4 dw screws through the shoes to attach the platforms. The lag screws are very robust, and I don't think my full weight on even just one of them would bend it.
I must say that I feel more secure in these than I do on any of the spike platforms, especially those real cheap nearly disposable spikes shoes that a lot of places sell.
These lace on nice and tight, and they're made from an old pair of my running shoes, so they're ubber comfortable. In fact they're sturdy and comfortable enough that I would use them in the Summer Olympics 100 Square Meter Epoxy Coating event**. Seriously, I've walked up inclines and stairs in these without a problem.
The one problem I do have is epoxy getting on the shoe laces - hate that.
If you're doing just one project it's easier to purchase a set. And regardless of the size of your project, I highly recommend using spikes - especially if you're using flakes.
** Almost as popular as Men's Synchronized Swimming!