Long and tedious ha. I use a good old fashioned hammer and crow bar, start from the top of the side with the least number of boards so that you can hammer off the 2x4 slats and loosen the other side without having to do as much work, it works most of the time but not always. I’ve got a sawzaw so next time I might try using the blade to cut through nails and see if that’s easier.
The best advice I can give is make the flag first and then build the table around the flag. Make sure all the boards for the flag are the same length. Not all of mine are and it made it a little tricky at the end. Thanks for the comment!