A dominant first half saw the hosts take the lead in Huelva after just 18 minutes when Isco curled home a superb effort from 25 yards in a one-sided Euro 2016 qualifier.
That advantage was doubled just under a minute later through Sergio Busquets' powerful drive, before Pedro wrapped up the win early in the second half.
The result leaves the defending European champions three points adrift of leaders Slovakia in Group C and in a strong position to qualify for the finals in France.
But Del Bosque, who made six changes from the win over Luxembourg, admitted that while he was pleased with the result, there were still some areas where his side could improve.
He was quoted by AS as stating: "We played well, we dominated the game and in less than half an hour we scored two goals.
"We wanted to play too narrow and too artistically. Isco played openly but he got caught up in the fine margins."
However, the 63-year old claimed the emphatic goals of Isco and Busquets could help improve the mood of his side, whO will need to be at their very best ahead of a stern test in the form of a friendly with Italy in March.
"We're not a team that usually gets goals from outside the box and we did here so that should boost morale," he added.
"The next target is March, against Italy...If we find the strength of that core we have a lot to look forward to."
