Image segmentation for each slice in a volume stack

I am trying to segment the largest boundaries in a cropped image for each slice in a volume. I am using imbinarize, applying a threshold, and then smoothing out the boundaries before using regionprops to calculate the areas of the blobs. I am having trouble getting to the point where I can have a list of areas for each slice in my volume. I believe only the last slice is getting outputted. Here is my code as of now

vol = tiffreadVolume('filename.tiff');

stack = vol(:, :, [224:2:276]);
stack = mat2gray(stack);

[a, rectout] = imcrop(stack(:,:,1))
for i = size(stack,3)
        img_crop = imcrop(stack(:, :, i), [rectout]);
        imshow(img_crop)
        binary_img = imbinarize(img_crop, 0.1);
        fill = imfill(binary_img, 'holes')
        area_filt = bwareafilt(fill, 5);
        imshow(area_filt)
        boundaries_trace = bwboundaries(area_filt);
        all_areas = regionprops(area_filt, 'Area')
        areas = [all_areas.Area];


end

Answer 1

[Matt J]

clear areas
for i = size(stack,3):-1:1
...
        all_areas = regionprops(area_filt, 'Area');
        areas{i} = [all_areas.Area];
end

[Jackie]

This worked great, thank you!