Lightly toast walnuts, almonds, pistachios, cashews and flax seeds separately without oil. Transfer it onto a plate and let it cool.
In a food processor or a mixer, add dates + apricots + nuts and seeds and process till all the nuts are coarsely grounds and everything comes together. (If you take the mixture in your hands and press, it should hold its shape. If not, grind again or add some more dates, apricot or raisins.)
Transfer into a rectangular tray lined with parchment paper or plastic wrap and press the mixture firmly and evenly. You could also grease the pan with clarified butter.
If you don't have any of the nuts, substitute that with the ones you have.
For dates or apricots, you can substitute with raisins, cranberries, figs or any soft dry fruits.
To get a smooth edge while cutting, grease the knife with oil or clarified butter.