Step 1: What You Need
1 1/2 yards of 54" wide patterned fabric
1 1/2 yards of 54" water resistant fabric
[wider fabric is fine - the size of your playmat is limited by the smaller of your pieces of fabric]
16 eyelets (mine were 5mm [a smidgeon bigger than 3/16"] )
5 yards of cord (must fit through your eyelets, my cord was 4mm)
iron & ironing board
eyelet setting tool, often included with the eyelets and hammer
Step 2: Cutting the Circles
Your playmat will be made from two pieces of fabric - a patterned piece and a plain water resistant piece, used as a lining.
My patterned fabric is lightweight curtain fabric and the water resistant lining is a coated nylon similar to that used for foldaway waterproof jackets.
The diameter of the patterned piece will need to be 5" larger than that of the lining, mine ended up at 54" & 49".
Cut each piece of fabric into a square and then fold into quarters. Keeping the centre of the fabric as the pointy end fold in half two times more so that you have a long skinny triangle. The centre of the fabric MUST be at the pointy end so that when you cut it you get a circle(ish) shape.
Place your tape measure so that the zero end is at the point and mark your radius as shown (radius = half of diameter, so my radii were 24.5" & 27"). Rotate your tape measure along the arc and make more marks as shown. Then join your marks into a smooth curve and cut along the line through all the layers. Depending on the thickness of your fabric you may need to cut the layers a few at a time. In this case place a weight on your folded fabric to help keep it together, a can of soup is good for this.
Open out your fabric and hey presto! you have 2 circles, one about 5" bigger than the other (2.5" bigger all round)
Step 3: Hem the Edge
Working on the wrong (back) side of your patterned piece mark a line 1" in from the cut edge, all the way around your big circle. Fold the raw edge in to meet this line and press with an iron set to the correct temperature for your fabric. Ease in the surplus fabric as you go and mind you fingers with the iron - turn off your steam to avoid scalded fingertips.
Now stitch the fold down, about 1/4" in from the fold.
Now mark another line 4" in from your fold and again fold your fabric in to meet this, and again press, giving a 2" hem. This time there will be more excess fabric to take care of, I pleated mine as I went around.
Fold your whole circle into eighths and press the folds firmly. Now unfold it all again.
Step 4: Insert the Lining
Lay your big hemmed circle right side down on the floor (or a bed, or wherever is big enough!) and insert your lining into it so the pressed hem folds over the whole edge of the lining. Make sure that the "outside" surface of the lining is on top. For my fabric the coated side was the underside against the patterned fabric. If you use oilcloth, the coated (prettiest) side should be on top.
Pin the 2" hem down all the way around and stitch all the way around twice. Your first line of stitching will be approximately on top of the stitching from step 3, your second will be about 1/4" to 1/2" in from the fold. These two lines of stitching hold the lining in place.
Step 5: Eyelets
Follow the instructions for your eyelet tool for making holes through all the layers at each marked point. My set had a hole punch for this, to be used with a hammer.
Then set in the 16 eyelets following the instructions for fixing the eyelets either using a hammer or a setting tool. I used dies A & 1 on my cropadile tool.
Step 6: Insert the Cord
Thread the cord though the eyelets. My polyester cord frayed as I tried to thread it so I melted the working end with a flame to seal it. If you are using cotton cord you may need to bind the end with tape to stop it fraying.
Ensure that the mat will lie flat BEFORE you cut the cord to length and make and extra few inches allowance for the knot. Thread both ends of the cord through the spring toggle and then tie the knot. Remember to heat seal the newly cut end if necessary.
Step 7: Play!
Simply spread the mat out to play on it - here it is complete with Lego. When your child (or you) have finished playing simply draw up the cord, slide the spring toggle up to hold the bag shut, tuck the excess cord inside the bag and hang the whole caboodle on the back of the bedroom door.