They work up in no time using a large hook and three strands of yarn.
Tips: Try to keep your stitches loose.
And the only thing I'd do differently is ch2 instead of ch3 to start new rows.
Round 6" Trivet-pattern from Fiber Flux-Please stop by to get a pattern for a square one and to see the great colors she used.
Using an N hook and three balls of 100% cotton yarn held together:
Chain 4, join with slip stitch.
R1~ Chain 3, DC into hole 11 times, join with slip stitch.
R2~ Chain 3, *DC in next hole, 2DC in next hole, repeat from *, join with slip stitch.
R3~ Repeat R2, fasten off and work in ends.