Glad you like the way these came out. I just used the HST's instead of a solid block for the four corners. The Missouri Quilt tutorial is good but I also have the book (from Connecting Threads).
The only trick is to get the HST's turned the way you want them to be in the finished block. I accidentally did it right the first time then pin-basted the others to be sure they ended up where I wanted them to be. Kinda blows the 10-minute block thing but I just happened to have the leftover HST's.
On the three-dimensional effect, I wouldn't want to leave that center piece unstitched. I sewed these down with a blanket stitch after I took those pictures. Seemed to add a little more dimension too.
These will probably become part of a small wall hanging for my sewing room.