Learn Icelandic: Við seljum alls konar einkennilega skrautgripi.

Even though alls konar is made up of words in the genitive case (meaning of all kind), it functions as an indeclinable phrase. It does not force the nouns and adjectives that follow it into the genitive. Here, einkennilega skrautgripi is in the accusative case simply because it is the direct object of the verb seljum.

Could I use the -s lags pattern taught in this lesson instead of alls konar?

Yes, you can use alls lags interchangeably with alls konar here. Both phrases mean all kinds of or all sorts of, and neither changes the declension or case of the following nouns and adjectives.

Why does the adjective einkennilega end in -a rather than -ir or -um?

It is modifying skrautgripi, which is a masculine plural noun in the accusative case. Strong masculine adjectives in the accusative plural take the -a ending. If they were the subject of the sentence (nominative), the ending would be einkennilegir.

What are the root words that make up the compound noun skrautgripi?