Start by cutting out 2 pieces of your main fabric 27 inches x 36 inches. Cut 2 more of the same dimensions out of your lining fabric.
Lay your two pieces of main fabric right sides together and sew the sides and bottom together using a 1/2 inch stitch.
Reach down into one corner of your bag and open slightly. Rotate the fabric so that the two sewn seams are now lined up one behind the other.
Lay the fabric back down and smooth out flat so that the seams are now at a 45 degree angle. Slide a ruler up the seam until you reach the spot that is 12 inches wide (obviously making sure 6 inches is in the center on the seam) and mark across with a disappearing ink pen or pencil. This is how wide the bottom of the bag will be, so if you are making it smaller you could also scale it back to about 10 inches.
Sew across that line and then cut off the point. I should mention that I reinforced all my seams with a zig zag stitch because I knew it would be holding a lot of weight and I didn't want the seams to rip or unravel. You could also just trim everything with pinking shears though.
Repeat with the second corner and this is the outside of your bag. Now go back and repeat all the previous steps with your lining fabric.
Once the lining is finished you can add a pocket for your phone and keys if you want. I didn't want to be fishing around for my keys for ten minutes, so I went ahead and used a piece of the fabric that I had cut off from the corner to make a small pocket. I'm not sure if it's really necessary or not to give instructions on making a pocket, but I took pictures anyway, because I'm the type of person that needs lots of pictures even if it is for something simple like a pocket.
Basically I took one of my squares that had been sewn together on two sides and cut off the bottom seam and then opened it up so I had one long rectangle piece. I sewed around all the edges to prevent unraveling, pressed them under and then stitched only across the top.
I pinned the fabric to the right side of my lining piece and then stitched it in place close to the edge along the sides and bottom.
And since my fabric already had a seam down the middle, I went ahead and sewed it to the lining along the middle seam turning it into two pockets. One for my phone and one for my keys.
Now pin your bag and lining right sides together and stitch around the top leaving a section open for turning it right side out.
Turn the bag right side out, tuck in the ends of the open section and press around the whole thing.
Pin the opening closed and top stitch around the top of the bag.
Now all that is left is the handles and I actually got these instructions from This Tutorial that was one that I found when I was looking for tote bag tutorials. If you want to know what this bag would look like in much smaller proportions than check out her adorable yellow stripped tote. The only difference between our bags other than the size is that my seams are on the sides and hers are on the front and back.
Cut out 2 strips of fabric that are 25 x 5. I originally made mine 30 inches long but when I pinned them to the bag I realized they were way too long. This was also the point where it was getting really late so I cut back on the picture taking. These are really simple though so I'm confident you can do it without a million pictures.
Measure in 3 inches from each end and mark with disappearing ink.
Fold the strip in half again and stitch along the edge in between the two dots.
Pin your handles where you want them on the bag (I measured in 8 inches from each side seam) and stitch to the bag in a square. I actually went around twice. Once right along the edge and again in about 1/8 of an inch just to make sure again that it wasn't going to come apart from the weight of all our beach supplies. Next sew an x from corner to corner of your box. Since it was late and getting dark I had to make myself a mark just so I could see where the corners were.
And that's it! Let me know if any of the instructions are unclear. Actually, it really helps to watch the video for the basket liner so you can see just how simple it really is.
And here is a little shot of our beach tote in action. Towels, snacks, floaties, and still plenty of room to throw in a baby. I mean diapers!