I am working this using Susan Newhall’s blended intarsia technique to make the sole doubled. I am not sure if this will terribly throw off the felting, but I’m willing to risk it.
I used a skein each of the colors and 2 of the grey. I have 75 g total left out of 300. Taking into consideration that doubled the yarn for the sole area which is the equivalent of about 25% of the felf, that means I used 125% of the yarn one would need at this gauge and for this yarn, or that 100% of the yarn that would be needed would be (0.8225 g) = ~180 g. Or, just under 4 skeins.
Felting took about 2 1/2 agitation cycles in my top-loader after a good presoak. A little pointy - that double sole really wants to hold its corners. Maybe if I do this again I’ll make the sole pattern more rounded.