I Bought Some Packets Of Ground Colombian Coffee...

[sandyRoe]

... thinking they were instant.  It makes a fine cup of java but there are grounds left in the bottom of the cup.

I guess it needs to be filtered.  How's that usually done?

 

[DDIL]

You can buy mini filters that sit on your mug, I use them when travelling.

https://amzn.eu/d/e63ULht

 

[Toorak]

You could buy a cafetière - since I started using one I never have instant coffee

[DDIL]

You put a couple of spoons of your ground coffee in it and pour freshly boiled water over it let it drip though and add more water as required.

[sandyRoe]

Thanks, both 

[Atheist]

Tea strainer. But proper coffee should be brewed for about 4 mins, so don't treat like a tea bag. A teapot would be OK if you first washed out the filthy tea taste.

[jack daniels]

I use a stovetop coffee maker which is good for using filter coffee, truly takes it into another dimension. I have a cafetière too. Easily buy some paper coffee filters as already suggested.

[sandyRoe]

I did buy a cafetiere and it does the job, but I think a tea strainer would have done just as well and been cheaper.

[gingejbee]

Do be careful with the glass beaker - they are very easy to break and cost a fair bit. (A friend supplies me with occasional 1 litre Pyrex laboratory tall-form beakers, which are the same thing).