First off the drive should be partitioned, possibly with fdisk. It should have atleast two partitions with one `EFI System` Partition and one `Linux filesystem` partition.
It should look something like this:
| Number of partition | Size | Type |
|:-----:|:-----:|:-----: |
| 1 | 1 to 2 GB or more | EFI System |
| 2 | Rest of the drive | Linux filesystem |
Then to create the filesystem of the efi partition.
```
# mkfs.fat -F 32 -n efi /dev/<disk1>
```
And the encrypted filesystem of the root partition.