I prewash all of my fabric... however, I did not prewash my background fabric because the fusible fabric was not prewashed. It should not make a difference in your end piece whether or not your background was prewashed.

Since this piece was bigger then my pressing surface, I like to use a spray baste to adhere my fabric to my pattern.

Mark the middle of your pattern.

Find the middle of your fabric... I do this by folding my fabric in quarters.

Spray baste evenly over 1/4 of your pattern ( you can spray either the pattern or your fabric) and then spread your fabric over the pattern making sure there are no lumps or bumps. Do this for the other 3 quarters as well.

You can now take your pattern to your pressing area without having to worry about things shifting!