Growing up in Amarillo, Texas, Lizzy Chesnut Bentley was rarely without her cowboy boots—a pink pair from her grandfather when she was 4 years old.

At Southern Methodist University in Dallas, where Ms. Bentley was president of the student Oil and Gas Club, she developed a reputation for helping students from out of state find their first pair of Texas cowboy boots and wearing her own favorite pair—vintage men’s two-tone ostrich boots she bought for $30—at sorority formals. By the time she was 24, she had amassed a boot collection 50 pairs deep, many of them vintage finds.

The footwear is both “functional and a fashion statement,” Ms. Bentley says. “You can wear them all day. You can put on jeans, and a white T-shirt, and a red pair of cowboy boots, and you have your outfit right there.”

After graduating in 2012 she moved to Houston to work at Halliburton as a financial analyst. The oil business was booming and she loved the city, where everyone she met seemed to be professionally driven. One element of corporate culture irked her, though: She couldn’t find a pair of cowboy boots that worked with her buttoned-up office wardrobe. “I’m wearing heels every day. I’m looking around, all the men are wearing cowboy boots, and I was just jealous,” she says.

Finally, she designed her own—of black buffalo leather with a single strip of white piping up the side—that she tucked into skinny black pants and wore with a blouse and a blazer.