The midfielder, 19, has represented Holland at youth levels and was close to joining the Cottagers in the summer.
Jol said: "He is an exciting talent but he will need at least six months of a year to adapt, but hopefully he will do it quicker. He is a very, very good talent.
"People say Ajax were interested and I imagine there will have been other clubs who were interested in him.
"We are very happy to get him. Maybe you can remember there was a little worry with his medical check on the last day of the transfer window so we decided not to do it.
"We took more time and that was a little problem for the boy because he couldn't play.
"First we have to get him fit and after that you will see he is an international player at all levels so I am very happy we have got him."