Pattern help circular needles

I’m knitting a Noni bag and this is the first time I have knitted in the round. I’m having difficulty understanding the pattern. I’ve casted on 80 stitiches and stiched in the round for the first 6 rounds, no problem on that. This is what I don’t understand - it says "turn and purl, rm, and continue by working back and forth “flat” in St st for 64 rows. Then join again, pm, and work in the round for 6 rounds.

How am I turning my work?
By removing the marker am I no longer joined? Don’t get how?
What is meant by working back and forth “FLAT”

Thank you

When you get to the end of the round, instead of going on to the next round, turn your work as if you were knitting on straight needles and purl the WS row. Work around to where you turned before and turn again to work the RS row. This is working flat rather than in the round, you remove the marker because you won’t need it until you work in the round again.

In a nutshell, the pattern wants a hole. So its telling you to stop working in the round and work back and forth like you would a scarf, so when you get to the row marker, turn your work so you can see the purls…purl till you get to the row marker, remove it, turn your work so you can see the knits, knit that row, turn again and continue like that for 64 rows…all still on the circular needle.
When you get done with the 64th row…turn again and you should be on a knit row…you would knit that row place marker and continue knitting in the round.

hope that helps…