These pre printed panels from Lecien's Cosmo 'hidamari' ('sunny spot') range have a fresh, contemporary style. These four coaster designs are printed on indigo blue cotton as a single panel, and include fabric to back the coasters (although you could draw more sashiko designs on these, and back them with another fabric to make a set of eight).  Instructions are in Japanese, but are pictorial and very easy to follow.

I first saw these coasters when we were in Osaka in January 2020, but due to lockdown, it has taken me a while to be able to order them. I'm not sure if I will be able to reorder though, so this might be the only time I can get them.
 
Finished of each coaster size approx 4in (10cm) square.

Marks wash out. NB - the marks have less contrast than my pre printed sashiko panels. The fabric is indigo colour, not natural indigo, so the colour won't run.

Designed and made by Lecien in Japan.
 
100% cotton.