It's been a while since I started mine. I went large scale, cutting 250 blocks and then being overwhelmed by the remaining material cost. I now plan on working on them at a slower pace, a few dz a year.
I would not recommend white foam. It can absorb water, unlike the closed cell pink or blue stuff. I bought my foam at a construction supply warehouse, since no one insulates homes in Miami.
I did a little variation on the technique, gluing 2 4x8 sheets together (gorilla glue and cinderblocks), then using a table saw and band saw to cut the blocks.
A few people have expressed concern over weight. The guy who introduced me to burlapped foamers did not put much weight (a single strap weight) in his blocks, and did not use a keel or tail board. They were VERY light, about on par with water keel plastics. That said, they worked great in calm water, but would likely roll over in open, choppy water. In my pile are a few dozen puddlers that I intend to make ultra-lightweight for walk-in hunts. The divers will have more weight for sure. I'm a little rougher with my dekes, so I may bolt on the keels.
For right now, I'm ordering Herter's heads. At $0.88, it's much easier than carving a bunch of heads (and about the same price). Eventually, as the Herter's heads get damaged, I'll replace with basswood heads.
Also, I've made some variations on the poses. I made a few puddler butts and a few standing decoys. You can also vary the attitude of the decoys with the tail and head.
Best of luck. As for me, I have some rasping to do!
Anyone can hold the helm when the sea is calm.
- Publilius Syrus (~100 BC)