There are, of course, many different ways to crochet a circle.When you make the end of a crochet circle,there is always a bumpy seam and gap which is easily visible. However, there is a easy and simple basic way to make a circle without gaps .This will give you a flat Seamless Circle.
Start your circle with a magic circle.I prefer using magic circle over the normal chain 6 and join method.
Magic circle would not give you the hole gap that can be seen in the middle of a circle.
You can check out the tutorial to make a magic circle here.
Make 12 Double Crochet in the circle.
Pull the short yarn end to close the circle and form a ring.
Slip stitch to the first Double crochet.
Now, here comes the trick to a seamless circle.Normally, you start a circle with chain three(which counts as a stitch), and continue with Double crochets in the following stitch.
So, instead of a chain three, start your round with a Standing Double Crochet.
Standing Double Crochet is nothing but to start your round with wrapping the yarn twice on the hook.
Check out the detailed tutorial on Standing double crochet at Crystals and Crochet.
To Start a Standing Double Crochet pull your hook up, making a loop that’s about the same height as a Double Crochet would be, and put your finger on the loop to hold it down.
Holding down the loop to the hook, yarn over the hook with the loop itself.
Now Yarn over the hook with your working yarn.
Next, still holding on to the top of that loop with your finger, pull the working yarn underneath the loop.
Now you can continue making your double crochet.
Work 2 Double Crochet in each stitch.
To close the round, instead of making a slip stitch in the standing double crochet, make a slip stitch in the Double Crochet which you have made.
This would give you a neat end.
Start your next round with a standing double Crochet.
Repeat 1DC, 2DC in all the stitches around.
Continue increasing your circle with the relevant number of stitches.
Now, doesn't it look neater than the normal chain three and join method??