To describe Straw Bale Gardening as a soil-less growing method isn’t strictly true. A small amount of soil or compost is used. However, it is a no-dig form of gardening.
The straw bale, or a hay bale (both would be suitable) is used as a raised bed. It has the advantage of being fully compostable when you’ve finished with it.
If you can easily and cheaply obtain straw bales this could be worth trying.
There is quite a lot of preparation involved but then that can be said of many gardening methods. You’d need to prepare the ground or the container whatever method of cultivation you choose.
The bales have to be soaked for up to ten days before you plant. For example, with a high nitrate liquid feed such as poultry manure.
You make a hole in the soaked bale, add some soil or potting compost so the plant’s roots have some support initially. Then plant your crops into the bale.
This growing method is not really suitable for root crops and tuberous vegetables like carrots, onions and potatoes. Mainly because there isn’t room for tubers to grow within the confines of the straw bale without a lot of regular effort from the gardener.