First, freeze the Biscoff spread until firm. That will make it easier to place into the cookie dough balls. Once you've made your cookie dough, if you find the dough quite sticky and difficult to manager, I recommend placing in the fridge to chill for 20-30 minutes. Use your thumbs to create a hole in each cookie dough ball and place the Biscoff inside there. Then use your fingers to cover the Biscoff completely.