These images are most likely made with one of two approaches:

1. Flat lay: the clothes are arranged flat on a large white surface and photographed from above.
2. Ghost mannequin variant: the clothing is placed on a mannequin, then additional shots are taken and combined in post so the garment keeps shape without the mannequin showing.

From the description, a flat lay shot from above is very plausible because the clothing appears flat. The even lighting suggests a fairly professional setup, typically using two lights from the sides with broad modifiers such as softboxes, umbrellas, or large reflectors.

To get the background completely white, use a large white seamless paper or white cloth and light it evenly. Keep the clothing well lit too, but avoid letting the subject blend into the background by controlling exposure and light placement. Final cleanup to pure white is often refined in post-processing.

So: likely flat on a white surface or a ghost-mannequin-style setup, lit broadly and evenly, with the final pure-white look finished in editing.