I'll definitely make several more pairs of these now I know how and I look forward to trying out different fabrics, prettier and more hard wearing but as prototypes (and my first attempt at making any kind of footwear) my main concern was not wasting money as well as time, so I restricted myself to only using materials and tools I already had. So for fabric I used a flannel shirt, just the sleeves, leaving the vest part intact and still wearable, but I'll most likely use it in some other project. For the soles of the shoes I used flip-flops (or thongs or whatever they're known as wherever you're reading this, they're both ridiculous names for what is a ridiculous excuse for a shoe) Between the outer and lining layers of fabric there is a nice thick layer of quilt batting; this is the secret to fooling ones feet into believing that they're still wrapped up in a duvet all day long, which on a cold day is exactly where they want to be. The batting I used was easily procured from a old pillow, with most cushions, pillows, and duvets it's possible to open the seams, peel back the cover and carefully separate the layers inside. Alternatively you could use several layers of old jumpers, blankets, or towels. Or you can go out and purchase quilt batting at a sewing supplies shop.
Any one reading this and contemplating making a pair for yourself I recommend making a rough pair like these just to establish a pattern that suits you then start thinking about using more attractive/ appropriate (expensive) materials for the the outer shell, I've found the flannel is suitable for a lining fabric, but also fleece or fake fur could be a great for extra warmth and comfort. I hear it's possible to waterproof fabric shoes with liquid latex or other paint on treatments, I haven't tried that yet.
If you find yourself without a pair of flip-flops but still want to sew your own shoes (like I am right now, those were my only pair) at the end I show how I took apart an old pair of hideously ugly boots to salvage the soles, those will be the base of my next project.
I believe the method I use here could be applied to making and attaching shoe uppers to any type of sole, for example high-heel shoes, or running shoes, and I intend on testing this theory in the near future.
Step 1: What I used
Soles: Flip-Flops (alternatively you may wish to salvage soles from an existing pair of shoes, refer to last step to see example)
Lining for Soles: I cut mine out of a strip of flannel around 17inches (44cm) long, and 11inches (28cm) wide.
Batting for shoe liners: 8x10in (21x26cm) I didn't use any in this example, but it can be easily added if extra cushioning is desired.
Upper Part of the shoe:
Fabric of choice - I used approximately 20x30 inches (52x77cm) that's sufficient for the outer shell and the lining, if you wish to use two different materials you'll need about 20x15 inches (52x38cm) of each.
Batting, I cut mine out of a piece about 20x10inches (52x26cm) and about 1.5 inches (4cm) thick.
When referring to these measurements consider that my finished shoe is 10in / 25cm long, 3.25in / 9cm wide. I am given to understand this is a ladies size (5-British) (38-European) (8-American) (24-Japanese) Adjust your measurements accordingly.
Tailors Chalk (or something else to mark fabric with)
Needle and Thread
Staple Gun and Staples (I used around 24 in total)
Hot Glue Gun & Glue Stick (I used about 4 inches of glue)
Fabric Glue I used only a tiny amount of this, you could probably use hot glue OR fabric glue, it may not be necessary to use both.
Paper I used 1-2 sheets of A4 printer paper, you may find graph paper helpful, newspaper would be fine too.
Sticky Tape (masking tape, sellotape or similar)
Pen (a sharpie or similar)