I was thinking...what is stronger, a blade made from flat stock or a damascus blade made from the same material? Why? If they were made and hardened and tempered the same which would be a better blade? Just a thought. It may change my plan for blade making.
Judging by the replies, the overall consensus seems to favor starting with flat stock of the appropriate thickness. I tend to agree.
It really depends upon your objectives when making the knife.
Heat treatment is the most important factor in a blade, and the best way to nail the heat treatment is to know the steel you're working with.
With modern steels, layering/welding the same steel upon itself would provide very little, if any, benefit. It won't make it any "stronger".
But, as mentioned, it can certainly introduce potential problems. Something else to keep in mind is potential carbon loss with repeated forging.
If aesthetics ("looks") are of primary importance in your blade, then I can see where "Damascus steel" would appeal to you.
We have many here who produce truly beautiful pieces of pattern-welded steel.
Besides the obvious labor involved, the different components must be able to take a good weld, and you'll have to come up with a good recipe for the heat treatment, since you're creating a new animal out of two different types of steel.
Depending upon the types of steel used, that can range from simple to next to impossible.
So you have to decide the goal of your blade, then determine how to achieve it.
If your primary goal is to retain the original known properties of the steel (strength, edge retention, etc.), the best way to keep those properties is to work with a piece of known stock and follow the appropriate heat treatment.