8.5 inches beautiful coaster which you can make even out of scrub yarn I like to use red heart yarn which is available at walmart https://www.walmart.com/search/?query=redheart%20yarn. It has many different usage such as on  a night stand, under a vase or on a coffee table, couple of them could be a nice gift will not take more than 45 min to make one.

all what you need to make this beautiful coaster are:

1- a size 3.5 crochet hook

2- size 4 yellow yarn

3- size 4 white yarn

4- spray starch

r1  in white yarn work 6ch join with sl st
r2  3ch(count as 1st dc) into the chain loop work 15dc (16) join with sl st in top of 3ch
r3  3ch(count as 1st dc) , *inc,dc* rep between *to* for the next 14 st join with sl st on top pf 3ch of the same round  fasten off do not cut yarn (24)
r4  join yellow yarn and work, 3ch(count as 1st dc) 1ch, {skip 1st then work *1dc, 1ch, 1dc into the next st* ,1ch} rep between {to }11 times , dc into the top of 3ch of r3 , 1ch, sl st into the top of 3ch of the same round (48)
r5  work sl st in to the next 2 stitches then 3ch ,dc, 1ch, 2dc into 1st 1ch space of r4. now work {1ch* into next 1ch sp work 2dc,1ch, 2dc*} rep between {to} 10 times, then work 1ch, sl st into the top of 3ch of same round (72)
 r6  sl st in to next 2 st, 3ch,1dc,1ch, 2dc, 1ch. now work {1ch * into next 1ch sp work 2dc,1ch, 2dc* } rep between {to} 10 times, then work 1ch, sl st into the top of 3ch of same round (72)
 r7  sl st in to next 2 st, 3ch, 2dc,1ch, 3dc, 1ch. now work {1ch * into next 1ch sp work 3dc,1ch, 3dc* } rep between {to} 10 times, then work 1ch, sl st into the top of 3ch of same round (96)
 r8  sl st in to next 3 st, 3ch, 6dc, now work {1ch * into next 1ch sp work 7dc*} rep between {to} 10 times, then work 1ch, sl st into the top of 3ch of same round fasten off and cut yarn (96)
finishing: work with white yarn that you left uncut as shown in the pictures below

 

 

 abbreviations 
 ch  chain
 sl st  slip stitch
 dc double crochet
 1st ch  first chain
 sp  space
 rep  repeat
 r  round
 inc  increase