I have often used straw bales as seating in my garden, but this takes the concept to an entirely different level. The photo seems to show an arrangement for a wedding, so it makes since that you want to protect people’s clothing as well as make them as comfortable as possible. If these were freestanding, you would probably need to provide some sort of support to keep the top bales from sliding off when people leaned back. The photo seems to show the sofas backed up against a hedge, which provides the support needed.
Even here in urban Los Angeles you can find straw bales for sale (or rent) at a nearby feed/lumber store. For one summer party I ordered in about 14 bales for seating all over the garden. It certainly brings a different feeling than the typical plastic chairs from the home store.
Previously in Garden Decor: