First, I'll show you a picture of the setup: each end has a 2x4 lying edgewise. A 2x6 lies between them, kinda like a bridge. I mis-measured the bed, so the 2x6 is too short; it doesn't reach all the way across. So I put a 2x4 on top of that.
As you can see, this creates a stand, or a prop, about 7½" high, which ought to be high enough. (If you make it too tall, you and everything else on the bed will tend to slide downhill—including the mattress.) How do you keep the 2x4s on the end from just collapsing onto their sides?
I did it wrong the first time; I drove screws through the 2x6 into the 2x4s, but the screws weren't long enough.
You can see the new and improved version at right; that bracket will hold the 2x4 on more securely. I also "toenailed" it in a couple of directions, and added a longer screw, too, through the top of the 2x6 into the edge or each 2x4.
And though the 2x4, lying down atop the 2x6, isn't subject to the same kind of sidewise pressures, I went drove two 2.75" screws through that long 2x4 into the 2x6, so it's a lot more stable than the old version.
The white things on the "foot" are felt pads; I thought they would be kinder to the floor than a 2x4 directly on it.
How about getting the thing under the bed? I used a hydraulic jack, as you can see below. With the bed being right next to the wall, there's not much room for a helper.
If you're wondering why we want to do this... well, let's just say there are lots of reasons why one might want to have the head end of the bed elevated.