Most people like to build the border first, then work on building up the inside of the puzzle.

So to do this you need to sort out the straight edges from the bulk of the pieces. If you are mixing all the bags then this is quite a lengthy task. It’s wise to do some other pre-sorting at this stage too. So while you are taking out the edges also sort the ‘inside’ pieces into main color groups. Putting then into empty ice cream containers (good because they have tight fitting lids and can be stacked – but other variations that have been used: buckets that are stacked inside each other at ‘tidy up’ time with the puzzle pieces still inside the bottom of each, cardboard Chinese takeaway boxes, rectangular clear take out food containers with lids, large plastic ziplock bags)

When sorting the edges – set aside separately the 4 corners when you come across them.

Build from the corners whenever possible, joining strings of pieces together. And matching the puzzle to the image on the poster/box lid.