There is always more to be said, but you may be interested in /u/mikedash's masterful answer to What are the chances the Vikings actually used the "Blood Eagle"?

TL;DR - Maybe.

There are precisely two mentions of the blood eagel from older sources, one in Orkneyinga saga and one in The tale of Ragnar's sons. Both were written hundreds of years after the christianization of Scandinavia and in turn refer to events hundreds of years before that. In fact, the reference in the Tale of Ragnar's sons is perhaps a viking fairytale in and of itself, there are some pretty serious doubts about the historicity of Ragnar Lodbrok. So maybe it happened, maybe it's just fiction ment to depict the Vikings as blood thirsty savages who would inflict death in the most horrifying manner imaginable.

This is one of those things historians can't really answer for you. The best we can do is say "we don't know". Vikings didn't leave many written records behind and the blood eagel is one of those things that leaves no archeological traces.

Alfred Smyth argues that it was a historical method of execution but bear in mind he is a specialist in medieval history of the British Isles, not Viking Age Scandinavia.

Roberta Frank on the other hand argues that the christian poets who wrote the surviving mentions we have simply misunderstood the kennings of scandinavian skalds for literal descriptions.

So what's a kenning? Well, it's a literary device of sorts, a circumlocution, a way of saying something with saying the exact word for it. In skaldic verse these could be quite complex and not always super intuitive to understand for the uninitiated. For example, a ship is simply a skip in old norse but in skaldic verse a kenning for ship could be gjálfr-marr (sea mare) or báru fákr (wave horse). A nice and even more complex example of this is from Thorbjorn Honklofi's Grymdrapa where the phrase "eyðendr arnar hungrs" occurs. Literally translated it means "enders of the eagels hunger". This is a reference scavengers feeding on battle sites, so the "enders of the eagels hunger" simply means warriors.

The most complex example I'm aware of is "fire-brandisher of blizzard of ogress of protection-moon of steed of boat-shed", again, a kenning for the simple word warrior. As we see here, they can be quite complex and hard to understand. Frank argues that the references to blood eagels are simply Christian poets who misinterpret older kennings as literally descriptions. Now, we don't know if "blood eagel" is a kenning but it could well have been. Frank argues that it is more likely a reference to leaving a slain enemy face down on the field of battle, his back exposed to the scavengers.