Depends on the layout of the sink and the construction of the cabinet and the look you are after too. If your 30" sink has has a cutout that exceeds the mfg spec of the 30" base you will have to go larger. Maybe post more info and more help will follow

First question: what kind of apron-front sink? Some are meant to sit atop a cabinet that's been cut down to recieve the sink. That'd be like the stainless steel or copper ones, and maybe some fireclay sinks with more regular rectangular shape. There's a thread on here (I think bichonlover started it) where Poorowner and I responded with pictures about our stainless apron front sink installations. Here's a picture of my sink. It's in a same-size cabinet with two dishwasher panels on either side. You could get away with not using the dw panels, but I needed them to deal with a spacing issue, and to cut down on dw noise. Some (and I'm thinking about the handmade Shaw's and other fireclay ones) are meant to go into an apron-front cabinet that's had a cutout in the blank apron front to receive the sink. Thus the cabinet has to be wide enough to hold the sink and still have some space on either side of the sink for the cutout. I think I've seen Shaw's owners with 33" sinks in a 36" cabinet, and the like.

Nicole: If the end pieces I pictured above were missing, you'd be looking at an exposed cabinet style and the top and bottom rail on each end and a hole between the three. The drawer end covers the void and makes your eye continue the line from the doors upward. A flush piece in the void would have to fit perfectly, be finished matched, would not continue the line, and would therefore look stupid. You're not going to find any pictures because no one would ever go through that much work for something that's not going to look good. Here's a full size 33" apron sink properly mounted in a 36" cabinet. The distance from the cabinet end to the sink apron end will be 3" on your job, not the 1 1/2" pictured here which I admit doesn't look too bad. That sink was replaced by this short apron Elkay Quartz Luxe. The bottom of the apron now lines up with the adjacent drawer bottom, and there is virtually no cabinet face exposed which I think looks better. I made the customer find a factory painted color match trim (you provide, you agree color matches) which I installed above and flush with the top of the middle rail to fill the gap. That didn't have to fit nearly as nicely as flush side fillers would have to, because only the person reaching under the sink will ever see it.

Thanks for the headsup, angela12345. I measured the GD and went to HD to measure the interior dimension of a 30" sink base cabinet. My oh my, a 30" sink base is TINY! But, it will have to do for now. The 33" sink base has more space inside and I wish we could put it in our layout without my being so bothered. Sigh. Alas, I really can't stand how the spacing of the sink base is uneven in relation to the already lopsided window on the wall. It makes me feel I am living in the winchester mystery house! So far, I have ascertained that it can hold our trash, recycle bin and compost pail, with a smidge of room left for fire extinguisher. Definitely no room for insta-hot water heater and filter. So, we nix that from our wish list. I am looking for a single bowl undermount. After some online research, I found a kindred sink KCUS30A-10/10BG that I like but I don't know if it's available online or not. I wish I could use the ticor sink but the one I like needs a 33" sink base. Bummer. The kindred sink I am interested in will have interior dimension of 27"W x 16"L x 10"H. I think that will work beautifully for washing my long-handled pans. Here's the specs: http://www.kindred-sinkware.com/grfx/products/specs/KCUS30A_10-10BG.pdf. Hope Kindred is a good product.