I've built a couple of these and they work well. They do need regular watering through the summer, and good soil. I initially didn't use good enough soil and the plants struggled. This year I'm getting a few good strawberries each day from 2 barrels.
I want to move them to a better spot for more sun and easier care, but am limited by garden layout.
They are made by cutting a horizontal slice in the the barrel (I used a circular saw) and then heating the plastic with a hot air gun to soften it, before ramming a wine bottle in to make the opening.
For next time; I would keep the top 12 inches of plastic free from openings and fill with soil to leave 6" of space at the top. Then I can water by quickly tipping a whole watering can on each one. With the openings near the top, water runs down the side and washes out through the planting holes.