I wanted to make a set of two placemats and two coasters for us to use when we were camping in our RV. Initially I used the free pattern from Red Heart for their Oval Placemat and Coaster.
Each of these placemats used about 105 grams of Lily Sugar 'n Cream worsted weight cotton yarn in the Country Side Ombre colorway.
After blocking, I wasn't able to get the placemat edges to lie flat, so I ended up cannibalizing the yarn to make my Simple Vertical Stripe Placemats instead, which ended up with interesting and unexpected plaid patterns due to the yarn color pooling. Totally an accident on my part; I didn't know beforehand that this yarn would do that.
The coasters do lie nice and flat, though, so I'm very happy with them.
I wrote up a free pattern on Ravelry for how I made these Simple Vertical Striped Placemats, but I wasn't able to explain in the pattern how to achieve the plaid pooling effect because -- again -- I don't know exactly how it happened. You can see in my above photo that the plaid effect you get depends on where in the color sequence you begin working. The one on the left turned out much closer to an argyle effect than the one on the right. If you want to attempt it, I wish you good luck and happy crocheting!!