Don't know how you can make freezer JELLY....
But to make seedless strawberry jelly you will have to cook the berries to release the juice and then drip it in a muslin jelly bag and make your jelly out of the resultant juice.
Linda C

As LindaC mentioned, the only way to get an absolutely seedless jelly is to drip the juice through a muslin bag. It's hard to find good jelly bags today. You can use a pillowcase or just go to a store that has a fabric section and get unbleached muslin. You need to suspend it so that gravity releases the juice in the bag. You can hang it off a knob with a bowl underneath or turn a stool upside down and tie a muslin square to the four legs (again with a bowl underneath). It will take about 24+ hours. For a clear jelly, don't squeeze the bag. If you only care about getting out the seeds and don't care about clarity, you can squeeze the bag. This will be less wasteful.

Without the seeds you lose a lot of the natural pectin. Freezer jams are already a fairly soft set. This will probably be a bit softer.

Carol

I have my Mom's old jelly bag........and the holder, the pointed colander and the old wooden thingy to go with it.
I think she got it in the early 1930's.
I will have to try making strawberry freezer jelly.

Well, the pointed colander (i.e. chinois or Chinese cap) isn't normally used for jelly. It's used to strain or puree things like squash. But it could work, so anything that does the job. You could use it to contain the jelly bag. I'm not sure the holes are fine enough to strain out the strawberry seeds otherwise.

Carol