porch furniture seat cushions?

I am a beginner sewer and am attempting to make my own seat cushions for some wicker porch furniture. Does anyone have suggestions for how/when to insert the foam and then finish up the cushion? I was thinking of machine sewing all but the narrowest side, sliding the foam in and then at that point I am kind of stumped... Can I finish the rest on the machine or do I need to hand sew it closed? All my projects up to this point have been following patterns.

Thanks for any advice!!

Always measure the fabric to the foam.  It's a lot easier to fit.  You need to cut a top, bottom, and four side panels.  Remember to leave a little ease (about 1/4 to 1/8th inch extra fabric on every piece you cut.  You can always make it smaller by increasing the seam allowances after you know it fits.  It's a lot harder to make it bigger, especially for a beginner. 

if you know how to insert a zipper, then do.  On a cushion it's easy.  Just sew it between a side panel and bottom or top.  Or, cut the side panel lengthwise across and sew the zipper between the two pieces.  With a zipper you will be able to insert the cushion without having to sew the foam into it on one side.   A zipper will let you remove the foam to wash your pillow.

If a zipper seems too difficult, sew all but one seam.  Fill with foam insert and hand sew the opening.

While sewing keep checking the fit against the foam to make sure.  (After doing this a few times, you won't have to anymore, but you're getting used to the three dimensional aspect of the foam. 

Good luck.

Great advice, thanks! Just cut my foam...now it is on to the fabric. Hopefully I can post some pics of my finished product soon!