Finally! The missing link between the cement bag and sitting on a cold and wet ground has been found! Not that there was the chain though... but who cares! Let's meke it!
Step 1: Clen
First of all take your bag and make it clean in any preferable way. This is the wowen-like plastic bag, and here in Ukraine we don't have a lot of those nicely graphically colored ones. So this one is just white.
Step 2: Cut
Cut the bottom where's the seam is (we'll make our own later). It's may be usefull to use a heated knife to prevent the unthreading.
Step 3: Cut Other Thing
Now cut the insulation for the inlay. I used 3 layers of 3mm foamed polyetheline sheets. It is waterproof, and has some stiffnes, and warm, and great, and beautifull, and I just had some laying around. But you can use something else. Just remember to make the sheet a little bit narrower and shorter in lenght than the bag we're crippled earlier to compensate the thickness of the material and to have ability to fold the bag edges for sewing (you'll get it later)
Step 4: Put Inside
Put the insulation into bag sleeve. I used... those clamping stuffs, to keep sheets together.
Step 5: Pin It Down
Fold the edges inside the sleave and above the insulation (see the photo) and secure them with pins or in some other way (do not use doble sided sticking tape for this, unless you're really hate yourself: it gums up the neadle and the thread making sewing nearly impossible... ...or use it if it is some sort of special sewing tape).
Step 6: Sew
Sew the edges with some strong synthetic thread... or anything you have lying around. But firstly you may want to try it on a test piece to ajust your sewing machine, or to make sure, it can handle this task at all (handstitching is always an option... a quiet painfull option, sometimes... but still an ption).
Step 7: Sew Again
Make the seams parallel to the long edge of the mat in aprox 1/3 of the mat's width from the edge... (just look at the photo). They will make the mat foldable this way, which is what we need for foldind it.
Step 8: And Again
To make the whole mat a bit more stiffer, sew any pattern you want all over thr place. It will also prevent the insulation from bunching inside.
Step 9: Lot of Sewing
Attach mysterious yellow straps to the back of your mat. It's much more better to have a fastex-type buckles on them, but this is what I had. Also you may use some rubbery stretchy strips instead. Or something completly different. I'm hete to inspite,not to dictate. It's not that hard to find out the right positioning for these pieces after you fold and roll the mat the way it supposed to be when stored.
Step 10: Fold and Roll
And this is how it's supposed to be rolled and folded... and stored. At the and I just pulled the yellow loops from the sides of the roll, but again, the fastex will be the best way to deal with it.
So this is it: The Foldable Bag Mat, you can make from a cement bag, and then fold it... and unfold... and sit on it... and be happy. Thank you for your attention, and ask me a question in the comments if I missed something in my guide.