The obvious difficulty when writing about pronunciation is that you have to hear sounds to imitate them. More than that, you sometimes need specific instructions as to how to recreate the sound, by becoming conscious of the position of your throat, tongue and teeth and whereabout in your mouth the sound is produced. Otherwise the natural tendency is to reproduce sounds that are similar but not the same in your own language, and that is what a “foreign” accent is, along with differences in speech rhythms and cadence.
Having said all of that, we’re going to have a go at describing the pronunciation of Spanish letters, starting with the A. As you know the letter A is called a vowel, which means it is an uninterrupted sound emitted from the throat. If I asked you to say what the A sound is in English, you would probably come up with either A as in SAY, or A as in CAT. You probably wouldn’t also include the sound of A in WHAT, CAR, ALL, ANY or MEDICAL. As English speakers, we tend not to notice what strange sound combinations our letters make, but these cause a lot of problems for foreigners learning our language.
The Spanish language doesn’t have these alternative sound and spelling problems. The letter A has one sound and one sound only. To give you an idea how to make the A sound, open your mouth nice and wide (almost as if you were saying “aaah” for the doctor, but not quite), but then cut that long “aaah” shorter to “ah”. You should end up with a sound that is not so far back and clipped as our A as in CAT, but about the same length! (I told you it’s impossible to write down sounds!) The letter A is always pronounced in this way, without exception.