I am testing out enabling flipping of non-square structures in v0.58.0. Right now it works with the Gold Refinery, the various Ore Refineries, and the Greenhouse. In order for the flip icon to appear, there actually has to be room for the flipped building.
Also if you play on a larger screen such as Desktop, there will be a new flip option before you commit your building queue, so that you can have buildings flipped before they are placed.
Finally, a simi-transparent preview of your queued structures now appears before you commit a build, so you can see what the pending product will look like before you start construction.