I have purchased ready-made bags made out of a frost cloth fabric and I use them a lot on both in-ground and container plants. They have a drawstring on the open end which makes it easy to kind of close them around the base of the plant too. So yes, I like your idea if you are crafty!

The drawstring seems like a smart idea!

I am handy but don't have much free time to make some. Realistically, it would take me hours to make just a small batch.

I saw shrub bags when I went online to buy my roll, but those were pretty big.

Are yours?

I have a variety of sizes. Some a shrub sized and some are smaller like the size of a pillow case. I can't seem to find the ones I have online. I will see if i can post a picture of one of the packages tomorrow.

That sounds like a good idea if you have the sewing skills, would be less expensive than buying the pre-made. Good winter project. I ordered these smaller frost blankets a couple weeks ago, I set them out today over the beets and leeks and they are a nice sturdy fabric, and the smaller size is so much easier to work with rather than a big roll of the stuff (my vegetable beds are only 4' wide):

https://www.groworganic.com/products/frost-blanket-ag-50-7-x-7-pk-of-5

How big around do your bags need to be? If you have used tomato cages and pillowcases... you can make pillowcases of the frost cloth by just cutting to the length you want and sew 2 sides shut to make the case. 6' around is a lot bigger than a pillowcase.

I would sew rather than glue or tape. Double stitch too, just for sturdy.

The pillowcases were actually too small. It's just all I had when I needed something.

I use a double layer. I just wrap the frost blankets, never thought about using my sewing machine before! I've cut my big frost blankets into appropriate sizes for what I need to cover. To hold them tight, I put an edge of the frost blanket under the row of pots on the front of the grouping of pots, same on the very back row of pots. Sometimes use large stones as well which might be good for your dahlias or empty pots to hold down the frost blankets. Then another layer over. I pull a small section of frost blanket & wrap a twist-em around it. That twist-em get hooked to a similar one that I've added at an appropriate place, so the 2 twist-ems get joined to hold the top together. Twist-ems come off easily. You mention tall stakes, which is what I use. I put enough stakes so the cloth floats over the plants.

A frost blanket will protect them from a light frost but I think a sheet of plastic somehow suspended over them-not touching the leaves would be better (or do both).