When a noun is modified according to a process that has been applied to it, how do we express this in Türkçe??? Is the process simply made into a verbal noun and the usual noun-noun descriptor rules applied or this a case for either the -li or -ik suffix?

For example:
"a burnt tree"
yanma ağaçı or yanlı ağaç or yanık ağaç

"a boiled egg"
kaynama yumurtayı or kaynalı yumurta or kaynalık yumurta

Mış, miş, muş, müş are used as suffixes for this. It's easy.I'll basically give the examples.

a burnt tree: yanmış ağaç
a boiled egg: haşlanmış yumurta (we use "haşlamak" for the food cooked in water)
an ironed shirt: ütülenmiş gömlek
an unironed shirt: ütülenmemiş gömlek
a used car: kullanılmış araba

etc., etc.

Notice that:
The verbs are made passive.
yanmak is already a passive verb in turkish. (ağacı yakmak: to burn a tree, but "ağaç yanıyor": the tree is burning)
haşlamak is to boil. haşlanmak is passive, but in english you use the same. to boil an egg: yumurta haşlamak; egg is boiling: yumurta haşlanıyor
ütülemek---ütülenmek
ütülememek---ütülenmemek
kullanmak---kullanılmak

thanks so much.. i too was unaware of this... thanks so much....really, i appreciate this a lot...

'yenmiş' and 'saklanmış' are correct.

It is better to accept yakmak and yanmak as two different verbs. Yakmak is "to burn" as in "Bu evi yakmak istiyorum" (I want to burn this house) and yanmak is "to burn up" as in "ağaç yandı" (The tree has burnd up).

Yakmak is the action who does burn something. Yanmak is the action of something that burns up. We can say "sıcaktan yanıyorum" (I'm burning from the hot weather, it is too hot for me). We can also say "İçim yanıyor" which means "my inside is burning (of unhappiness or regret)". So I think it is better to accept "yanmak" as a different verb.

Yakmak has a passive form which is yakılmak (to be burnt).

Bu ağacı yakacağım.
Bu ağaç yakılacak.

sağolun hocam