I tape one side to my cutting table. Then I dampen the panel and gently 'persuade' a second side to conform to the 90 degree angle of the table. That side gets taped down. I continue doing this until all 4 sides are taped down. Then I spray it to make it quite wet and leave it to dry. It's my go-to method and, while time consuming, it has worked well for me.

What a great method!

Donna Jordan at Jordans Fabrics has a good you tube on panels and straightening. Do a search. I will see if i have it saved.

Thank you so much for posting this site. I learned so much from the video. I will book mark it for later reference. I use panels to make wall hangings for each month of the year.

I have only used a very few panels in my quilting career. One I cut around the design and appliqued that main piece to a baby quilt. Another I bought to use as you are trying to do and had limited success. I tell myself I need to try again. I know I will be successful and am confident. I keep looking but haven't found the perfect panel. I would think sashing might even out the borders even if the sashing has to be a bit awkward as long as it is not noticeably off. I like some of the suggestions here and will put them to use possibly when I do another panel.