Step 1: Materials
Thread (I'm using gutermann sew all)
Filling (Rice/Wheat/Feed corn/Buckwheat hulls/Barley/Oatmeal/Beans/Flax seed/Cherry pits)
Two pieces of a 100% cotton material roughly 14cm wide and 50cm long.
Essential oil (I've used lemon scent)
Because this project will be going in the microwave, a material that won't melt in heat is essential. For that reason I've specified 100% cotton. My favourite is flannel/flannelette/winceyette as this has a soft and slightly cosy texture while still being cotton.
"Fat eighths" are particularly good for this sort of project, especially when you have a lot of them in your stash.
Step 2: Filling Preparation (optional)
I did, and so I put the rice I'll be using into a sealable bag and then added several drops of essential oil to it to my own tastes for how strong a scent I would like. It will dissipate some once it has been put into the heatable bag, so keep this in mind when adding the oil.
Seal the bag and leave to marinate for as long as possible before use. I usually go for some time between 4 days and 3 weeks depending on how organised I am.
Step 3: Pinning
If you're a bit scatterbrained you may find it useful to mark with a pencil or disappearing marker a gap of about 4cm that you'll be leaving open when you sew.
Step 4: Sewing
Depending on how confident you are in your skill, aim for a seam from between 0.5cm and 1cm. I usually use a 1cm seam, but go as low as 0.5cm when my fabric is less wide than usual.