Fruit – Substitute frozen cranberries for fresh berries

You might consider trying slicing them in half first, so at the very least, they're not a round sphere that's liable to roll away. Here's the typical procedure for cherry tomatoes, grapes, pitted olives, etc:

1. Place a few of them on your cutting surface (as many as would fit comfortably in the palm of your hand
2. place the palm of your non-knife hand on top of the items.
3. arc your fingers up as best you can
4. slice horizontally with a very sharp knife, parallel to your hand and the cutting surface.

If that's small enough, stop, otherwise pile up a bunch of halves, and run your knife through like anything else.

I found a site with another cranberry sauce maker complaining of the end product being too runny. What I learned is that cranberries have lots of natural pectin that is released when they are cooked past bursting.

If it were me, I would:

1. cook it some more, keeping it at a boil but watching it carefully so it doesn't boil over and does not start to scorch at the bottom of the pan (in other words, stir and WATCH IT!)
2. When the cranberries have deflated from releasing their inards and some of the excess liquid has either boiled off or thickened, your recipe should be salvageable.

Best of luck!