Some words have doubled consonants which do not follow a short, stressed vowel

They make words longer (and thereby automatically more difficult for beginners) and they undermine the reliability of doubled consonants that serve a phonic function, as in

  accurate,  daffodil,  rebellious, comment, annual, opposite, tomorrow, professor, forgotten.

They also mislead inexperienced readers to place stress on the wrong syllable, instead of the vowel which carries it (underlined):

Accommodate, accommodation, accompany, accomplish, accord, accordion, account, accumulate, accuse, accustom, occasion, occupation, occurrence, succumb;  

affection, afford, paraffin, affair, affect, effect, efficient, differential, diffusion, offend, official, sufficient, chauffeur;

llama, parallel, really, excellent, hello, jewellery, marvellous, satellite, constellation, caterpillar, illegible, illiterate, illusion, illustration, illuminate, pastille, tonsillitis, collage, collapse, collect, collide;

ammunition, programme, immediate, immense, immortal, immune, command, commemorate, commence, commercial, commit, commodities, commotion, communication, communion, community, commuter, committee, recommend; 

anniversary, announce, annoy, connect, personnel, mayonnaise, questionnaire;

appal, apparatus, apparent, appeal, appear, appendix, applaud, apply, appoint, appreciate, apprentice, approach, appropriate, approve, approximate, hippopotamus, opportunity, oppose, supply, support, suppose;

arrange, array,  arrest,  arrive,  barricade, erratic, interrupt, serrated, terrific, irregular, irrigation, torrential, correspond, correct, correlation, hurrah, curriculum, surrender, surround;

assail, assassin, assault , assemble, assert, assessment, assign, assist, associate, assort, assume, cassette, embassy, dessert, essential, necessary, possess, possibility;

battalion, tattoo, mattress, attach, attain, attempt, attend, attention, attorney, attract, attributed, omelette, palette, settee.

 

O  is often not as in spot.

It can sound like the u in cup, oa in toast, oo as in book or oo in boot and e as in herb

Among, block, blond, blot, bob, bog, bomb, bond, boss, both, bottle, box, brother, clock, cobble, cock, cod, comfort, control, cop, cot, crop, cross, dock, dodge, dog, doll, don, dot, drop, enrol, fishmonger, flock, flog, flop, fog, folk, fond, fox, frog, from, front, ghost, gloss, gobble, god, goggle, golf, gong, got, gross, hobble, hog, hop, host, hot, job, jog, jostle, jot, lob, lock, loft, log, long, lop, lot, mob, mock, Monday, mongrel, monk, monkey, month, mop, moss, most, mother, nod, not, nothing, nozzle, off, on, once [wunce], only, other, ox, patrol, plot, pod, pond, post, poster, pot, prod, prop, rob, rock, rod, roll, romp, rot, scroll, slog, slot, smock, smother, snob, sob, sock, soft, solve, son, song, sponge, spot, stock, stop, stroll, strong, sword, sworn, throttle, to*, today, tomb, ton, tongs, tongue, top, topple, toss, tot, trod, troll, trot, whom, wobble, wolf, womb, won, wonder, word, work, world, worm, worn, worry, worse, worship, worst, worth.

 

O-e  is often not as in bone, solo or so,  but like u of cup,  o of hot,  short oo of wood,

          long oo of soon,  er of her,   i of bit)

Above,  adolescence,  alcove,  alone,  altogether,  anemone [anemmony],  antelope,  approve,  arose,  beloved,  benevolent,  bone,  broke,  choke,  chose,  chosen,  close*,  closet,  clover,  code,  colonel,  colour,  come,  comedian,  comedy,  comet,  component,  compose,  composer,  cone,  cope,  cove,  covenant,  cover,  covet,  covey,  devote,  discover,  discovery,  dispose,  doe,  does,  dole,  dome,  domestic,  done,  dose,  dove,  doze,  dozen,  drone,  drove,  elope,  envelope,  expose,  froze,  frozen,  globe,  glove,  goes,  gone,  govern,  grocer,  grope,  grovel,  gruesome,  handsome,  hole,  holey,  home,  honest,  honey,  hope,  hose,  hover,  impose,  improve,  insolence,  insolent,  joke,  Joseph,  lone,  lonely,  lose,  love,  lozenge,  mode,  model,  moderate*,  modern,  modest,  mole,  moment,  monetary,  money,  move,  node,  none,  nose,  note,  novel,  November,  October,  omelette,  omen,  one [wun],  open,  opera,  operate,  operation,  oven,  over,  phone,  poke,  pole,  pope,  pose,  postpone,  poverty,  primrose,  process,  procession,  profession,  professor,  promenade,  promote,  proper,  property,  propose,  protein,  prove,  proven,  proverb, pullover,  purpose,  quote,  recover,  remote,  rhinoceros,  robe,  rode,  role,  rope,  rose,  scone,  scope,  shone,  shove,  shovel,  slope,  slovenly,  smoke,  sober,  sole,  solemn,  some,  somersault,  sovereign,  spoke,  spoken,  stoke,  stole,  stolen,  stone,  stove,  strode,  stroke,  suppose,  syndrome,  tadpole,  those,  throne,  together, tomorrow,   token,  tolerate,  tone,  trombone,  vote,  whole,  whose,  woke,  woman,  women,  wove,  wrote,  yodel,  yoke,  zone,

do,  to,  two, who.

 

OO  is short, not long as in spoon, in:

Book, brook, cook, cookie, foot, good, hood, hook, look, rook, shook, stood, took, understood, whoosh, wood, wooden, wool, woollen.