take a bic pen and a bottle. hold a lighter to the bottle, untill a hole starts to melt, when it is still smaller than the bic, quickly take the lighter away and force the sharp end of the bic through the hole. it will make a hole perfectly shaped for a bic as a stemm. then to get an air tight seal, wrap scotch tape once around the middle of the bic. after you gut the bic and put a bowl on it, slide it in the bottle untill the tape is halfway into the hole, then put water in up to under the whole. vwallah, you've got an airtight slider.