Any clue on how to get plain dm-crypt booted?

[avdb]

I have /dev/sda which is partitionless with plain dm-crypt set-up but I can't seem to get it to boot. Note that unlike LUKS encryption to open plain dm-crypt block devices you have to specify the cipher and hash used, otherwise it'll be impossible to retrieve the logical volumes. I have to specify this somewhere in my GRUB kernel parameter file but I have no clue where. The Gentoo Wiki only provides this article but there isn't a single piece of information that can help me out. Other than that it also seems like block devices don't have UUIDs or labels to specify which block device you want to decrypt.

[eccerr0r]

Solution is to use partitions. It's needed to install grub for MBR or the ESP for EFI.
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Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?