As to Poelkapelle : Tom is correct. Except that the -e at the end is pronounced too. (As in your article "the", or the first vowel in "ago".)
As to Graventafel. Not easy to explain without using phonetical writing. (Which I could not type !)
First sound G- is something that does not exist in English. Certainly not the same as in Grave ! It's a sound deep in the throat, certainly in the kind of Dutch spoken in Holland. (But didn't G.B. Shaw call that sort of Dutch : not a language, but a throat disease ?
But don't worry if you cannot produce it. For we here, in our Province of West-Flanders, cannot pronounce it either. We make it an H. Like in Home. Try that one, and no one here will even notice that it is not correct !
Both -a-'s : very close to your -a- in "father", "path", "last", "calm", "palm". Our long -a- in Standard Dutch however is more palatal (hard part of the palate), whereas yours is more velar (soft part of the palate)
And both -e-'s are as in your article "the", or first vowel in "ago".
And the stress is on the first syllable.
Next time we meet (Tom and others), make sure you have done your homework !
Aurel