Hey,
Finger print without border means the box should not be visible when you scan it. Only the signature should be seen. The dimensions of the box is given so that you can understand the size of the signature you have to do. If it wasn't given than it would be very confusing for candidates to sign on a blank paper.
So, just scan the signature, without any box and resize it to 10-50 kB and upload it in JPEG/JPG format only.

Hope this helps!