I made one for DS 1 - heres how it goes
Get a sheet of sunday times/guardian similar broadsheet
lay it into your buggy with the top of the sheet where you want the top of the snuggle to be and pin it on at the top.
Press paper into seat to get width right,folding in any excess and fold up any excess when you're happy with how much the bottom hangs over the foot end .
Mark where your straps are with a felt tip. take paper off buggy and cut the excess off, round off the corners
This is your pattern for the underneath of the snuggle. For the top get another sheet of paper and cut it to come two thirds of the way up the underneath pattern and cut it 6 inches wider than the underneath(so there's leg room)
measure your pattern pieces and buy enough fleece to suit,a lining of your choice, a zip to go round the top part if you want and some binding twice the all round measurement of the back if using a zip,enough to go round the top one third of the back,across the front and down 4-6 inches of the sides if not
No zip version
cut both pattern pieces out in fleece and lining,marking slits for staps and sew fronts to backs, right sides together ,leaving 4-6 inches of the top unsewn at the sides for flap
place lining inside fleece (all seam edges between layers) make sure nothing's twisted and sew round the raw edges (across front,down flap,back up and round back and back to where you started, Bind edges however you prefer(by hand/machine) and zigzag round marked slits then cut through (like giant buttonholes)
If wished sew a bit of velcro each side so you can fold the flap up when it's cold
I'll post the zipped one if anyones interested
Lisa X