The standard way to start a round of double crochet (dc) stitches is to make 3 chains. Then, when you come back around to finish the round, you slip stitch to the top of the chain-3 and then make another 3 chains to start the next round.
The problem is that the ch-3 does not look like the rest of the double crochet stitches in the round, and the slip stitch to join the row creates a noticeable gap. The result is a seam running straight across your otherwise beautiful piece.
One alternative is to join with an invisible seam and then start each row with a Standing Double Crochet (Sdc) instead. Watch this video for a demonstration, or visit this link for written instructions: https://www.changepathcrochet.com/how....