I know it's sacrilege (don't shoot me!), but for sitting still in cold weather, wool is junk. Base layers don't matter. And layering makes no difference. Let me explain.
Wool has it's place for other roles, but keeping one warm when idle is not it. You can't wear enough of it; trust me, I've tried. That's why you see so many folks recommend things like the HBS, super-insulated pac boots, and electric or chemical warmers.
Think about this: why don't you see wool sleeping bags? Because it is not a great insulator for keeping an idle person warm! The best cold-weather insulation is down! I have a couple different-thickness down puffy jackets to wear as a midlayer, and some Primaloft insulated pants. And with those alone, I can be comfortable wearing uninsulated rubber boots and usually even no gloves!
Warmth is thickness. My "big" down puffy has about 1" of loft. Whether that inch of loft comes from 8 layers of heavy wool (good luck affording that, much less moving underneath it!), or 32 layers of magic wicking poly base layers, or any combination, it's all the same warmth. But no material on earth provides more loft for less weight than down.
I've tried everything else, and have since sold my nice woolens, and never been more comfortable in the stand. I know you're supposed to wear wool if you're on TradGang, but it just doesn't work in the treestand! And you can shop online sales (or Costco) for down jackets cheaper than just about any other more common hunting substitute.
Pete