Ronald Koeman made no less than five changes from the 1-1 draw against Cadiz, with Sergio Dest, Clement Lenglet, Ousmane Dembele and Antoine Griezmann on the bench.
Barcelona should've gone in front in the early seconds through a curling strike from the near side by Francisco Trincao, but goalkeeper Edgar Badia read the danger and parried.
The visitors launched a scare of their own moments later with a snap-shot in the centre of the area from Lucas Boye following a loose ball, but Barca survived the threat.
Then astounding bit of trickery in the centre of the area from Trincao towards the midway stage produced a one-hand save off Badia following a curling shot.
Elche continued their stubborn approach late in the first half after Boye cleared a dangerously looking free-kick from Lionel Messi away.
A double substitution from the Blaugrana ahead of the second half saw Dembele enter from the bench ahead of Miralem Pjanic.
Barcelona made their dominance count seconds later when Messi started a move with Martin Braithwaite from the near side before going on to find the bottom-corner.
Messi had a double towards the last 20 minutes after he picked up a low ball from the left by Frenkie De Jong to apply a composed finish from the near post amidst a few challenges.
It got worse for Elche on 72 minutes when a knockdown from the inside-left channel by Braithwaite picked out Jordi Alba to volley beyond Badia.
Barcelona were in the mood for more following the closing period, but substitute Griezmann particularly failed to pounce however three goals proved enough.