Vori 
Welp, from what I read the firecracker kernel has no FUSE support, which means I have to compile the kernel myself
I did it, but now it doesn't see the root drive in /dev/vda...
FINALLY found the solution...
You can't actually use the normal linux kernel, but you have to clone the amazon linux kernel fork with microvm branch...
After cloning you have to create a .config with config downloaded from them firecracker documentation
This will work, but still no FUSE support
So you need to add these lines to .config
CONFIG_FUSE_FS=y
CONFIG_CUSE=y
CONFIG_VIRTIO_FS=y
CONFIG_OVERLAY_FS=y
After compiling it should work
You can't actually use the normal linux kernel, but you have to clone the amazon linux kernel fork with microvm branch...
After cloning you have to create a .config with config downloaded from them firecracker documentation
This will work, but still no FUSE support
So you need to add these lines to .config
CONFIG_FUSE_FS=y
CONFIG_CUSE=y
CONFIG_VIRTIO_FS=y
CONFIG_OVERLAY_FS=y
After compiling it should work