When I have sown Callistephus chinensis outdoors or indoors/green house I just covered them lightly with some soil. Nothing special needed at all. As I recall they grow rather slowly at first, so don't think they should get to an unmanageable size before you can plant them out if sown now. Outdoors horticultural fleece is efficient to keep birds away and helps with germination of many seeds, providing a sheltered micro climate, but not sure what squirrels would do with that.
Not heard of scarification in the freezer before, is it possible that it should be stratification??? In any case I fail to see why placing seeds dry in the freezer would be beneficial, but perhaps something I missed. Generally if we are talking about stratification, seeds needs to be placed in a moist media and usually they are kept in temperatures just above freezing as frost sometimes can damage them when they are moist. It usually takes a lot more time than five days as well. Many times one will first also sow them at warmer temperatures to let the seed absorb more moisture before the cold period in the refrigerator or outdoors.
