The Dutchman has already captured centre-back Fernando Amorebieta, midfielder Derek Boateng and goalkeeper Maarten Stekelenburg on free transfers.
Goal exclusively revealed on Saturday that Jol is planning a fresh bid for Tottenham midfielder Tom Huddlestone following a failed January swoop while they close in on the capture of Wolves star Bakary Sako, and Jol is hoping to secure more recruits sooner rather than later.
|22/1||Fulham are 22/1 with bet365 to finish in the top six next season
"We are still working on one or two - we want them going with us as well. There will be one or two coming back, because we had a few loan players. I'll try to get them in now, because 14 players are left and we're still working on five or six players to come to this club.
"Three are already here so that was good, because most of the time you do your business late. This was quite early, so that was a positive sign."
Fulham are set to play three pre-season friendlies against Costa Rican Primera sides including one against Bryan Ruiz' former club, Alajuelense.