I don't think this can be done in Lightroom. You'll need a program like Photoshop to do that.
There is no selection and cut/copy/paste tools in LR and no way to combine a second image.
At least none that I am aware of.
I use a tri-fold white board display. (bought at Target) and place the item on small foot stool with plenty of light and flash. I hope this helps.
Hello, what is the simplest way to make a white background for product photos? thank you
Depends what you are trying to do.
If you just want to place one picture on a white background you can use the Slideshow module. This also allows you to add text in the picture. When your layout is done go to top menu Slideshow> Export JPEG Slideshow.....
If you want to place multiple items in the same picture the Print module will work. In the Print module under 'Layout Style' select 'Picture Package' or Custom Package.' Design your layout and under 'Print Job' select 'Print to:' JPEG.