Macbook pro (mid-2012) startup chime delayed (slow booting) after HDD to SSD conversion
Avoid cloning a HDD to a SDD
The problem with cloning is that you are making an exact copy of all the data on your drive at the block level - including the deleted data.
Spinning media acts and breathes differently than solid state media (i.e. TRIM support) and as such, you will be introducing problems for your SSD where none existed on the HDD.
What do do instead?
Do a clean install and utilize Migration Assistant to transfer your user data.