English spelling/pronunciation example

Question

I think most of us can agree, English pronunciation vs spelling (vs conjugation) is strange:

Read (present tense)
Read (past tense)
Red (color)
Reed (plant)

contrast with

Lead (direct, present tense)
Led (direct, past tense)
Lead (the metal)

... however, I'm currently teaching Japanese students English, which generally makes no distinction between L and R-based sounds. Is there any similar set(s) of words I could use as an example that would avoid this potential confusion? I'm trying to make each sets' differences more obvious audibly. Ideally, new sets have some similarity/difference in different conjugations of a verb (something irregular); I'm hoping for "related" results. Probably, the stranger the better.
I speak (probably standard) North-West American English, if this makes a large difference.

---

EDIT:

To forestall too many questions about what sounds Japanese "natively" supports, here's the sounds usually used in transliteration to English. Note that everything ends in a vowel (whose sounds are constant, and pronounced identically as in Spanish). Not having a given sound doesn't mean it can't be heard - it just means that distinguishing between it and the "nearest neighbor" is difficult/impossible. I probably only need to replace one set, so something without an L/R sound is what I'm looking for.

Answer 1

Sure, there are more oddities you could use:

• eat (present), ate (past), eight (number)
• say (present), said (past), saying (present participle), saying (noun, meaning "proverb")
• sell (present), sold (past), cell (noun), solder (noun, not pronounced as one may first think)
• throw (present), threw (past), through (preposition)
• know (present), knew (past), no (negation), new (adjective)
• dive (present), dove (past), dove (the bird)
• sew (presented), sewn (past participle), sewer (noun, meaning "tailor"), sewer (noun, meaning "drain")

Moreover, these could lead to some interesting practice sentences:

He ate eight pancakes.
His love for her knew no bounds and was new every day.
I am saying a very wise saying that was said long ago.
The dove dove toward the ground.
He sold the solder to the soldier in the cell.
He threw the newspaper through the window.

Answer 2

-ough words are great for these kind of eye rhyme.

Dough and Though are pronounced the same, but spelled differently,

While you'll get Through, Tough, Bough, Trough, and many other alternative -ough pronunciations despite them all having the same suffix.

Answer 3

I think this is actually a problem of phonetics. What you need is professional know-how how to teach the clear pronunciation of l and r to speakers of languages where this opposition is not in their language system. Such speakers have to know where the tip of the tongue is positioned in the mouth cave and that the tongue stays attached to the frontal gum. There is special literature on phonetics where the articulation is described.

The production of a frontal r is much more complicated as the tip of the tongue touches the gum shortly and disconnects at once. If I had to teach such things to speakers of South East Asia I would have to think about designing diagrams of these articulations, of real models of the mouth room, and of special articulation exercises. But I know the task is no easy one.