I make several types of earth boxes.
These instructions are for using a plastic planting pot - the kind you'd buy at a nursery or garden center. I believe I got these years ago at a large big box hardware place with an orange & white logo.
It should take you less than an hour to convert one of these into a container suitable for herbs.
Another post will show you how to make the big 20 gallon ones I use for tomatoes, cucumbers, peppers, zucchini, watermelon. etc.
Here is part one...
Here is part two...