There are many tutorials on it, but, some are making it much harder than it needs to be. The trick is where to connect the squares. If you start with a simple square (cut 6" for finished 5 1/2") and attach a 5" square of interfacing to one side, it will be easy to turn them right side out and do a bit of topstitching. I use 950F interfacing because I prefer the body without the stiffness. I like to do a simple stitch 1/8" in and then do a decorative X stitch thru the square. It is not necessary, but I think it helps keep the shape when stored away.
The trick is to measure down 1" from one corner (both directions) and at the opposite corner measure up 3". If you connect a 1" mark with a 3" mark, you will see the stitch lines to connect with the next square. I sew them together in 6 sets of 2, then add sets so I have 3 sets of 4, then put the rest together. When you lay it flat you will see where you tack the 'petals' together and perhaps add a button or other embellishment. If you look on Pinterest, you will see pictures of the square with the 1" and 3" markings. Trust me, it sounds funny but when you put the first one together, it will make sense. Once you do one, then you can play around with sizes (the 5 1/2" will finish at an 18" wreath) and with banding one of squares and with making a smaller size. Smaller is a bit more difficult so I suggest start with this size. BUT, CAUTION, making them becomes addictive! Have fun!