If you want to see what the blanket looks like, you could either spread it out over two or more circs, if you have them, or lace a piece of yarn through all the stitches and spread it out.
Stitch holders don’t come that big. I actually find that I don’t use them anymore because their stiffness gets in the way. I use yarn instead. I’ve found, too, that very often when I have to take the stitches off the stitch holders they’re on the wrong way (the yarn is at the wrong end) so I have to switch them back and forth between needles. A Pain.
Stitch holders look like big safety pins, and I haven’t seen any longer than about 5 to 7 inches. But as I said, since they aren’t flexible, they sometimes get in the way when you’re knitting around them. Waste yarn works just fine.