If the blocks are just foundation pieced, ie stitched onto a piece of gash cotton, muslin etc. as it seems they are from what you have said in your last post, then you just sew them together to a size you can confidently quilt, .... then QAYG those blocks with the joining strips.
As it is a scrappy quilt I suggest that it might be fun to have different sized blocks for the QAYG process.
For instance I QAYG The HSTathon in 6 equal blocks but it was a very regimented pattern ...for a scrappy string quilt a more eclectic layout would look fun.... lets me see if I can draw something up.
Make sure the joining strips are either dark to 'disappear or bright if you want to emphasise the randomness of the layout.
You will need to decide your layout;
Sew the blocks together until you are happy you can manoeuvre the size they are under your machine
and put them together like a jigsaw on the floor to ensure they become the shape and size of the finished quilt
you want them to be (maybe number them at this stage)
Now layer them ... backing cut bigger than the wadding, wadding cut bigger than the top.
Lay the backing out wrong side up, then wadding, now the top right side up
Now pin or spray baste with 505.
Finally take each block and have fun quilting it...
and lastly, using the method shown in the tut, join the QAYG blocks together in rows and then join the rows together.
It can be a bit cumbersome at the end when you are joining two rows to three rows etc but slow and sure will do the job.
More help here ...
https://youtu.be/ji8BLS2rNHA?t=1