How can I get full-length ‘shadowless’ portrait photography?

I have little experience in this field of photography. I would like to get a “shadowless” photo on a gray background. An example of what I want I found on the Internet:

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My results are unfortunately bad. I use two 180×120 softboxes and radio synchronizer. One softbox was placed right in front of the target another softbox 45 degrees from the target. They are set to the same power. I use Canon EOS 5D Mark III with Canon EF 24-70mm f/2.8L II USM lens. I upload simple example (ISO 100, F9, 1/125). Although the photo is slightly underexposed

enter image description here

The photo was unsuccessful. As I understand it is surely the wrong scheme of light. But I can not understand how to achieve a shadowless effect as at the top of the photo. And of course my photo doesn’t look like a contrast compare to others.