This is a quick and easy block if you stitch it down by machine. I don’t like to mess with the settings on my machine in order to use a heavier thread so I fuse the pieces to the background fabric and couch over another thread with a narrow zig zag stitch. I’ve used a couple strands of floss (or a single strand of perle cotton), button/carpet thread, crochet cotton and even fingering weight yarn. It would just depend on how much you want the outline to stand out.
Don’t like fusible backing or don’t have any on hand? Elmer’s school glue (washable!) works great as a temporary hold. I also use this glue for turning under raw edges. It’s not real tacky but a small dab plus a quick press with the iron keeps it in place quite nicely.
The size of background fabric required isn’t stated for this block but the tulips are 3″ x 4″ and if placed in the corner as shown on the pattern an 8″ square would suffice.