Welcome to the Quilting Board!
Using my cell phone camera and lots of labels works for me, too. It is so frustrating to get them out of order.
I have a small sewing area and small house without a wall for even a wall to hang a design wall. I lay out a flannel sheet on a table then lay out the blocks. Since I rarely have time to finish the assembly I have taken pictures which I really like. Then I fold up the sheet over the blocks carefully. I can unfold as I am ready to work on the top.
I do both suggestions, pinning to keep in order and marking with sticky notes.
I like your flannel sheet idea, Newby. If you fold carefully or roll it up you could unfold a row at a time as you sew.
I have wooden clothes pins. I mark each one by row and number,apply to the blocks in order,then it's easier to keep them where they should go. I'm famous for sewing stuff upside down and backwards...repeatedly!
Life may not be the party we planned for,but while we are here we should dance!
I use the small yard sale type stickers with the A, b, c, going down and numbers going a cross. A-1, A-2 etc. I also take pictures a a rearrange them and finally after I settle on the final layout.
No need for fancy pins - if you have flower head pins you can write on the "flower" part with a sharpie