Take a long (30ft) length and put several loops around her chest (both above and below her breasts). Each loop should also go round her upper arm in a figure of 8 pattern, so her arms are pinned by her side.
Help her to lay on her back then get her to draw her legs up as far as is comfortable while still keeping her feet on the bed/floor. Then use short lengths of rope to tie her left wrist to her left ankle and her right wrist to her right ankle. A spreader bar is optional, but will make her nicely exposed for you.
http://www.japanrope.com/tutorial.html is also worth a browse to see if it gives you any more ideas.
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