Here's one Dawn that looks really easy!
Hi Dawn, I hope this video helps you
Do you want to build just the trundle drawer to fit under an existing queen sized bed, or build a whole new queen sized bed with trundle storage?
Unless you already have all the requisite tools and lumber, it may be more cost effective to purchase a ready-made one.
here are some instructions for you https://www.simplicityinthesouth.com/make-built-in-trundle-bed-cabinets