Option 1 (Total fee 47 GBP+ Airport car parkfee) - simple way
by taxi from Airport Stansted to Hackney
takes approx. 45 to 60 min
call taxi and book in advance +44 2072543030

Option 2 (Total fee 30 GBP) 
by Express Train from Airport Stansted to Liverpool Station, departure of train every 15 min, duration 47 min, standard single ticket approx. 24 GPB
https://www.stanstedexpress.com/?tid=airport or by the ticket in the train, then by underground duration 20 min, first Circle Line -> King's Cross, then change to Victoria Line -> Highbury & Islington, then change to Overground -> Dalston Kingsland, day ticket approx. 6 GBP, then by food 7 min

Option 3 (Total fee 15 GBP)
by Express Bus from Airport Stansted to Liverpool Station, departure of train every 15 min, duration 55 min, standard single ticket approx. 9 GPB
http://www.stanstedairport.com/transport-and-directions/buses-and-coaches#CoachestoLondon,  then by underground duration 20 min,
first by Underground Circle Line -> King's Cross
then change to Victoria Line -> Highbury & Islington
then change to Overground -> Dalston Kingsland
day ticket approx. 6 GBP, then by food 7 min

by car Calais - Dover 
take the ferry, departure approx every 1,5 hour, ONLY if book by internet one day in advance approx. 60 GBP with car for single travel fee http://www.poferries.com/ then by car to London approx. 1,5 hour to Hackney.