Literally.
Cut the shirt right below the armpits, both layers. Zig-zag stitch around the opening, leave the already-hemmed bottom as the edge that shows, and you have a stretchy tube-belt. Good support, good coverage for that peek-a-boo tummy.
$1.25 for t-shirt from thrift store vs. $30+ range for the original.
Almost embarrassing to admit, but I really, really like these. Now. For me. And my NOT-pregnant-just-chunky, shirts-not-quite-long-enough-for-my-current body.
VERY convenient. Does wonders for modesty so you can stretch without showing skin. Nice with pants, skirts. See the above photo, that darker, under shirt, that was once a t-shirt. Biggest advantage is how low you can wear it, without the layers and heat of a tank top.
Find the stretchiest, smallest tshirt that will fit around your waist. Cut. Try it on. Most of the t-shirt knits do not need to be zig-zagged if they do not unravel, so you can wear it as is.