I use 10 loci Memory Palace for this .
Place 4 letters per loci.
5 loci = Edges
5 loci = Corners
LIST of BLD letter pair
I am sharing my some letter pairs list.
A
Aa - Aam (mango)
Ab - Abacus
Ac - Acid
Ad - Adapter
Ae - Aeroplane
Af - Afeem (opium)
Ag - Agnibann (fire arrow)
Ah - Ahilya
Ai - Air balloon
Aj - Ajooba
Ak - Ak 47
Al - Alien
Am - Ambulance
An - Antenna
Ao - Aorta
Ap - Apollo
Aq - Aquarium
Ar - Art
As - Astronaut
At - Atm
Au - Auto
Av - Avocado
Aw - Award
Ax - Axe , Ashtray
B
Ba - Baal (hair)
Bb - bubble
Bc - bicycle
Bd - Beeds
Be - Belt
Bf - Beef
Bg - Bug
Bh - bee hive
Bi - billy (cat)
Bj - beej (seed)
Bk - book
Bl - blade
Bm - bomb (bum)
Bn - bun
Bo - Board
Bp - bp machine
Bq - bouquet
Br - bra
Bs - bus
Bt - button
Bu - bull
Bv - beaver
Bw - bowl
Bx - box , bushes
I don’t quite understand your math here… you got 8 corners and 12 edges… why do you need to memorize 20 letters for corners and another 20 letters for edges?