“I wanted to have a butcher’s so I took a Dublin packet and slapdash, a bracket-faced seven sided animal gave me a dub o’ th’ hick.”

Let’s dissect:

butchers:  Cockney slang meaning look.  Cockney slang, or rhyming slang, was most prevalent in the East End of London.  It consists of replacing a word with the beginning portion of a rhyming phrase.  For example:  substituting ‘look’ with ‘butcher’s hook’ but dropping the ‘hook.’  It may have risen to wide use as a way to keep outsiders from a close community (Wikipedia).

Dublin packet:  turn a corner; to ‘take the dublin packet” viz run around the corner – probably a pun on doubling a corner (A dictionary of modern slang, cant, and vulgar words by John Camden Hotten)

Slapdash:  Immediately, instantly, suddenly. (1811 Dictionary of the Vulgar Tongue by Francis Grose)

Bracket-faced:  Ugly, hard-featured (1811 Dictionary of the Vulgar Tongue by Francis Grose)

Seven sided animal:  you know this one 😉

dub o’th’hick:  A lick on the head (1811 Dictionary of the Vulgar Tongue by Francis Grose)

So, to sum up “I wanted to have a butcher’s so I took a Dublin packet and slapdash, a bracket-faced seven sided animal gave me a dub o’ th’ hick”  means “I wanted to take a look so I turned a corner and suddenly an ugly one eyed man gave me a lick on the head.”